FETCHMAIL(1)              fetchmail reference manual              FETCHMAIL(1)



NAME
       fetchmail - fetch mail from a POP, IMAP, ETRN, or ODMR-capable server


SYNOPSIS
       fetchmail [option...] [mailserver...]
       fetchmailconf


DESCRIPTION
       fetchmail is a mail-retrieval and forwarding utility; it fetches mail
       from remote mail servers and forwards it to your local (client)
       machine's delivery system.  You can then handle the retrieved mail
       using normal mail user agents such as mutt(1), elm(1) or Mail(1).  The
       fetchmail utility can be run in a daemon mode to repeatedly poll one or
       more systems at a specified interval.

       The fetchmail program can gather mail from servers supporting any of
       the common mail-retrieval protocols: POP2 (legacy, to be removed from
       future release), POP3, IMAP2bis, IMAP4, and IMAP4rev1.  It can also use
       the ESMTP ETRN extension and ODMR.  (The RFCs describing all these
       protocols are listed at the end of this manual page.)

       While fetchmail is primarily intended to be used over on-demand TCP/IP
       links (such as SLIP or PPP connections), it may also be useful as a
       message transfer agent for sites which refuse for security reasons to
       permit (sender-initiated) SMTP transactions with sendmail.


SUPPORT, TROUBLESHOOTING
       For troubleshooting, tracing and debugging, you need to increase
       fetchmail's verbosity to actually see what happens. To do that, please
       run both of the two following commands, adding all of the options you'd
       normally use.


              env LC_ALL=C fetchmail -V -v --nodetach --nosyslog

              (This command line prints in English how fetchmail understands
              your configuration.)


              env LC_ALL=C fetchmail -vvv  --nodetach --nosyslog

              (This command line actually runs fetchmail with verbose English
              output.)

       Also see item #G3 in fetchmail's FAQ
       <https://fetchmail.sourceforge.io/fetchmail-FAQ.html#G3>.

       You can omit the LC_ALL=C part above if you want output in the local
       language (if supported). However if you are posting to mailing lists,
       please leave it in. The maintainers do not necessarily understand your
       language, please use English.


TLS (SSL) QUICKSTART
       Your fetchmail distribution should have come with a README.SSL file,
       which see.  It is recommended to configure all polls with --ssl
       --sslproto tls1.2+ if supported by the server, which configures
       fetchmail along recent IETF proposed standards and best current
       practices, RFC-8314, RFC-8996, RFC-8997.


CONCEPTS
       If fetchmail is used with a POP or an IMAP server (but not with ETRN or
       ODMR), it has two fundamental modes of operation for each user account
       from which it retrieves mail: singledrop- and multidrop-mode.

       In singledrop-mode,
              fetchmail assumes that all messages in the user's account
              (mailbox) are intended for a single recipient.  The identity of
              the recipient will either default to the local user currently
              executing fetchmail, or will need to be explicitly specified in
              the configuration file.

              fetchmail uses singledrop-mode when the fetchmailrc
              configuration contains at most a single local user specification
              for a given server account.

       In multidrop-mode,
              fetchmail assumes that the mail server account actually contains
              mail intended for any number of different recipients.
              Therefore, fetchmail must attempt to deduce the proper "envelope
              recipient" from the mail headers of each message.  In this mode
              of operation, fetchmail almost resembles a mail transfer agent
              (MTA).

              Note that neither the POP nor IMAP protocols were intended for
              use in this fashion, and hence envelope information is often not
              directly available. The ISP must store the envelope information
              in some message header and. The ISP must also store one copy of
              the message per recipient. If either of the conditions is not
              fulfilled, this process is unreliable, because fetchmail must
              then resort to guessing the true envelope recipient(s) of a
              message. This usually fails for mailing list messages and Bcc:d
              mail, or mail for multiple recipients in your domain.

              fetchmail uses multidrop-mode when more than one local user
              and/or a wildcard is specified for a particular server account
              in the configuration file.

       In ETRN and ODMR modes,
              these considerations do not apply, as these protocols are based
              on SMTP, which provides explicit envelope recipient information.
              These protocols always support multiple recipients.

       As each message is retrieved, fetchmail normally delivers it via SMTP
       to port 25 on the machine it is running on (localhost), just as though
       it were being passed in over a normal TCP/IP link.  fetchmail provides
       the SMTP server with an envelope recipient derived in the manner
       described previously.  The mail will then be delivered according to
       your MTA's rules (the Mail Transfer Agent is usually sendmail(8),
       exim(8), or postfix(8)).  Invoking your system's MDA (Mail Delivery
       Agent) is the duty of your MTA.  All the delivery-control mechanisms
       (such as .forward files) normally available through your system MTA and
       local delivery agents will therefore be applied as usual.

       If your fetchmail configuration sets a local MDA (see the --mda
       option), it will be used directly instead of talking SMTP to port 25.

       If the program fetchmailconf is available, it will assist you in
       setting up and editing a fetchmailrc configuration.  It runs under the
       X window system and requires that the language Python and the Tk
       toolkit (with Python bindings) be present on your system.  If you are
       first setting up fetchmail for single-user mode, it is recommended that
       you use Novice mode.  Expert mode provides complete control of
       fetchmail configuration, including the multidrop features.  In either
       case, the 'Autoprobe' button will tell you the most capable protocol a
       given mail server supports, and warn you of potential problems with
       that server.


PREFACE ON THIS MANUAL
       Fetchmail's run-time strings have been translated (localized) to some
       languages, but the manual is only available in English.  In some
       situations, for comparing output to manual, it may be helpful to switch
       fetchmail to English output by overriding the locale variables, for
       instance:


              env LC_ALL=C fetchmail # add other options before the hash


              env LANG=en fetchmail # other options before the hash

       or similar. Details vary by operating system.


GENERAL OPERATION
       The behavior of fetchmail is controlled by command-line options and a
       run control file, ~/.fetchmailrc, the syntax of which we describe in a
       later section (this file is what the fetchmailconf program edits).
       Command-line options override ~/.fetchmailrc declarations.

       Each server name that you specify following the options on the command
       line will be queried.  If you do not specify any servers on the command
       line, each 'poll' entry in your ~/.fetchmailrc file will be queried,
       unless the idle option is used, which see.

       To facilitate the use of fetchmail in scripts and pipelines, it returns
       an appropriate exit code upon termination -- see EXIT CODES below.

       The following options modify the behavior of fetchmail.  It is seldom
       necessary to specify any of these once you have a working .fetchmailrc
       file set up.

       Almost all options have a corresponding keyword which can be used to
       declare them in a .fetchmailrc file.

       Some special options are not covered here, but are documented instead
       in sections on AUTHENTICATION and DAEMON MODE which follow.

   General Options
       -? | --help
              Displays option help.

       -V | --version
              Displays the version information for your copy of fetchmail.  No
              mail fetch is performed.  Instead, for each server specified,
              all the option information that would be computed if fetchmail
              were connecting to that server is displayed.  Any non-printable
              characters in passwords or other string names are shown as back-
              slashed C-like escape sequences.  This option is useful for
              verifying that your options are set the way you want them.

       -c | --check
              Return a status code to indicate whether there is mail waiting,
              without actually fetching or deleting mail (see EXIT CODES
              below).  This option turns off daemon mode (in which it would be
              useless).  It does not play well with queries to multiple sites,
              and does not work with ETRN or ODMR.  It will return a false
              positive if you leave read but undeleted mail in your server
              mailbox and your fetch protocol cannot tell kept messages from
              new ones.  This means it will work with IMAP, not work with
              POP2, and may occasionally flake out under POP3.

       -s | --silent
              Silent mode.  Suppresses all progress/status messages that are
              normally echoed to standard output during a fetch (but does not
              suppress actual error messages).  The --verbose option overrides
              this.

       -v | --verbose
              Verbose mode.  All control messages passed between fetchmail and
              the mail server are echoed to stdout.  Overrides --silent.
              Doubling this option (-v -v) causes extra diagnostic information
              to be printed.

       --nosoftbounce
              (since v6.3.10, Keyword: set no softbounce, since v6.3.10)
              Hard bounce mode. All permanent delivery errors cause messages
              to be deleted from the upstream server, see "no softbounce"
              below.

       --softbounce
              (since v6.3.10, Keyword: set softbounce, since v6.3.10)
              Soft bounce mode. All permanent delivery errors cause messages
              to be left on the upstream server if the protocol supports that.
              This option is on by default to match historic fetchmail
              documentation, and will be changed to hard bounce mode in the
              next fetchmail release.

   Disposal Options
       -a | --all | (since v6.3.3) --fetchall
              (Keyword: fetchall, since v3.0)
              Retrieve both old (seen) and new messages from the mail server.
              The default is to fetch only messages the server has not marked
              seen.  Under POP3, this option also forces the use of RETR
              rather than TOP.  Note that POP2 retrieval behaves as though
              --all is always on (see RETRIEVAL FAILURE MODES below) and this
              option does not work with ETRN or ODMR.  While the -a and --all
              command-line and fetchall rcfile options have been supported for
              a long time, the --fetchall command-line option was added in
              v6.3.3.

       -k | --keep
              (Keyword: keep)
              Keep retrieved messages on the remote mail server.  Normally,
              messages are deleted from the folder on the mail server after
              they have been retrieved.  Specifying the keep option causes
              retrieved messages to remain in your folder on the mail server.
              This option does not work with ETRN or ODMR. If used with POP3,
              it is recommended to also specify the --uidl option or uidl
              keyword.

       -K | --nokeep
              (Keyword: nokeep)
              Delete retrieved messages from the remote mail server.  This
              option forces retrieved mail to be deleted.  It may be useful if
              you have specified a default of keep in your .fetchmailrc.  This
              option is forced on with ETRN and ODMR.

       -F | --flush
              (Keyword: flush)
              POP3/IMAP only.  This is a dangerous option and can cause mail
              loss when used improperly. It deletes old (seen) messages from
              the mail server before retrieving new messages.  Warning: This
              can cause mail loss if you check your mail with other clients
              than fetchmail, and cause fetchmail to delete a message it had
              never fetched before.  It can also cause mail loss if the mail
              server marks the message seen after retrieval (IMAP2 servers).
              You should probably not use this option in your configuration
              file. If you use it with POP3, you must use the 'uidl' option.
              What you probably want is the default setting: if you do not
              specify '-k', then fetchmail will automatically delete messages
              after successful delivery.

       --limitflush
              POP3/IMAP only, since version 6.3.0.  Delete oversized messages
              from the mail server before retrieving new messages. The size
              limit should be separately specified with the --limit option.
              This option does not work with ETRN or ODMR.

   Protocol and Query Options
       -p <proto> | --proto <proto> | --protocol <proto>
              (Keyword: proto[col])
              Specify the protocol to use when communicating with the remote
              mail server.  If no protocol is specified, the default is AUTO.
              proto may be one of the following:

              AUTO   Tries IMAP, POP3, and POP2 (skipping any of these for
                     which support has not been compiled in).

              POP2   Post Office Protocol 2 (legacy, to be removed from future
                     release)

              POP3   Post Office Protocol 3

              APOP   Use POP3 with old-fashioned MD5-challenge authentication.
                     Considered not resistant to man-in-the-middle attacks.

              RPOP   Use POP3 with RPOP authentication.

              KPOP   Use POP3 with Kerberos V4 authentication on port 1109.

              SDPS   Use POP3 with Demon Internet's SDPS extensions.

              IMAP   IMAP2bis, IMAP4, or IMAP4rev1 (fetchmail automatically
                     detects their capabilities).

              ETRN   Use the ESMTP ETRN option.

              ODMR   Use the On-Demand Mail Relay ESMTP profile.

       All these alternatives work in basically the same way (communicating
       with standard server daemons to fetch mail already delivered to a
       mailbox on the server) except ETRN and ODMR.  The ETRN mode allows you
       to ask a compliant ESMTP server (such as BSD sendmail at release 8.8.0
       or higher) to immediately open a sender-SMTP connection to your client
       machine and begin forwarding any items addressed to your client machine
       in the server's queue of undelivered mail.   The ODMR mode requires an
       ODMR-capable server and works similarly to ETRN, except that it does
       not require the client machine to have a static DNS.

       -U | --uidl
              (Keyword: uidl)
              Force UIDL use (effective only with POP3).  Force client-side
              tracking of 'newness' of messages (UIDL stands for "unique ID
              listing" and is described in RFC1939).  Use with 'keep' to use a
              mailbox as a baby news drop for a group of users. The fact that
              seen messages are skipped is logged, unless error logging is
              done through syslog while running in daemon mode.  Note that
              fetchmail may automatically enable this option depending on
              upstream server capabilities.  Note also that this option may be
              removed and forced enabled in a future fetchmail version. See
              also: --idfile.

       --idle (since 6.3.3)
              (Keyword: idle, since before 6.0.0)
              Enable IDLE use (effective only with IMAP). Note that this works
              with only one account and one folder at a given time, other
              folders or accounts will not be polled when idle is in effect!
              While the idle rcfile keyword had been supported for a long
              time, the --idle command-line option was added in version 6.3.3.
              IDLE use means that fetchmail tells the IMAP server to send
              notice of new messages, so they can be retrieved sooner than
              would be possible with regular polls.

       -P <portnumber> | --service <servicename>
              (Keyword: service) Since version 6.3.0.
              The service option permits you to specify a service name to
              connect to.  You can specify a decimal port number here, if your
              services database lacks the required service-port assignments.
              See the FAQ item R12 and the --ssl documentation for details.
              This replaces the older --port option.

       Note that this does not magically switch between TLS-wrapped and
       STARTTLS modes, if you specify a port number or service name here that
       is TLS-wrapped, meaning it starts to negotiate TLS before sending
       application data in the clear, you may need to specify --ssl on the
       command line or ssl in your rcfile.

       --port <portnumber>
              (Keyword: port)
              Obsolete version of --service that does not take service names.
              Note: this option may be removed from a future version.

       --principal <principal>
              (Keyword: principal)
              The principal option permits you to specify a service principal
              for mutual authentication.  This is applicable to POP3 or IMAP
              with Kerberos 4 authentication only.  It does not apply to
              Kerberos 5 or GSSAPI.  This option may be removed in a future
              fetchmail version.

       -t <seconds> | --timeout <seconds>
              (Keyword: timeout)
              The timeout option allows you to set a server-non-response
              timeout in seconds.  If a mail server does not send a greeting
              message or respond to commands for the given number of seconds,
              fetchmail will drop the connection to it.  Without such a
              timeout fetchmail might hang until the TCP connection times out,
              trying to fetch mail from a down host, which may be very long.
              This would be particularly annoying for a fetchmail running in
              the background.  There is a default timeout which fetchmail -V
              will report.  If a given connection receives too many timeouts
              in succession, fetchmail will consider it wedged and stop
              retrying.  The calling user will be notified by email if this
              happens.

              Beginning with fetchmail 6.3.10, the SMTP client uses the
              recommended minimum timeouts from RFC-5321 while waiting for the
              SMTP/LMTP server it is talking to.  You can raise the timeouts
              even more, but you cannot shorten them. This is to avoid a
              painful situation where fetchmail has been configured with a
              short timeout (a minute or less), ships a long message (many
              MBytes) to the local MTA, which then takes longer than timeout
              to respond "OK", which it eventually will; that would mean the
              mail gets delivered properly, but fetchmail cannot notice it and
              will thus re-fetch this big message over and over again.

       --plugin <command>
              (Keyword: plugin)
              The plugin option allows you to use an external program to
              establish the TCP connection.  This is useful if you want to use
              ssh, or need some special firewall setup.  The program will be
              looked up in $PATH and can optionally be passed the host name
              and port as arguments using "%h" and "%p" respectively (note
              that the interpolation logic is rather primitive, and these
              tokens must be bounded by whitespace or beginning of string or
              end of string).  Fetchmail will write to the plugin's stdin and
              read from the plugin's stdout.

       --plugout <command>
              (Keyword: plugout)
              Identical to the plugin option above, but this one is used for
              the SMTP connections.

       -r <name> | --folder <name>
              (Keyword: folder[s])
              Causes a specified non-default mail folder on the mail server
              (or comma-separated list of folders) to be retrieved.  The
              syntax of the folder name is server-dependent.  This option is
              not available under POP3, ETRN, or ODMR.

       --tracepolls
              (Keyword: tracepolls)
              Tell fetchmail to poll trace information in the form 'polling
              account %s' and 'folder %s' to the Received line it generates,
              where the %s parts are replaced by the user's remote name, the
              poll label, and the folder (mailbox) where available (the
              Received header also normally includes the server's true name).
              This can be used to facilitate mail filtering based on the
              account it is being received from. The folder information is
              written only since version 6.3.4.

       --ssl  (Keyword: ssl)
              Causes the connection to the mail server to be encrypted via
              SSL, by negotiating SSL directly after connecting (called SSL-
              wrapped mode, or Implicit TLS by RFC-8314).  Please see the
              description of --sslproto below!  More information is available
              in the README.SSL file that ships with fetchmail.

              Note that even if this option is omitted, fetchmail may still
              negotiate SSL in-band for POP3 or IMAP, through the STLS or
              STARTTLS feature.  You can use the --sslproto option to modify
              that behavior.

              If no port is specified, the connection is attempted to the well
              known port of the SSL version of the base protocol.  This is
              generally a different port than the port used by the base
              protocol.  For IMAP, this is port 143 for the clear protocol and
              port 993 for the SSL secured protocol; for POP3, it is port 110
              for the clear text and port 995 for the encrypted variant.

              If your system lacks the corresponding entries from
              /etc/services, see the --service option and specify the numeric
              port number as given in the previous paragraph (unless your ISP
              had directed you to different ports, which is uncommon however).

       --sslcert <name>
              (Keyword: sslcert)
              For certificate-based client authentication.  Some SSL encrypted
              servers require client side keys and certificates for
              authentication.  In most cases, this is optional.  This
              specifies the location of the public key certificate to be
              presented to the server at the time the SSL session is
              established.  It is not required (but may be provided) if the
              server does not require it.  It may be the same file as the
              private key (combined key and certificate file) but this is not
              recommended. Also see --sslkey below.

              NOTE: If you use client authentication, the user name is fetched
              from the certificate's CommonName and overrides the name set
              with --user.

       --sslkey <name>
              (Keyword: sslkey)
              Specifies the file name of the client side private SSL key.
              Some SSL encrypted servers require client side keys and
              certificates for authentication.  In most cases, this is
              optional.  This specifies the location of the private key used
              to sign transactions with the server at the time the SSL session
              is established.  It is not required (but may be provided) if the
              server does not require it. It may be the same file as the
              public key (combined key and certificate file) but this is not
              recommended.

              If a password is required to unlock the key, it will be prompted
              for at the time just prior to establishing the session to the
              server.  This can cause some complications in daemon mode.

              Also see --sslcert above.

       --sslproto <value>
              (Keyword: sslproto, NOTE: semantic changes since v6.4.0)
              This option has a dual use, out of historic fetchmail behaviour.
              It controls both the SSL/TLS protocol version and, if --ssl is
              not specified, the STARTTLS behaviour (upgrading the protocol to
              an SSL or TLS connection in-band). Some other options may
              however make TLS mandatory.

              Only if this option and --ssl are both missing for a poll, there
              will be opportunistic TLS for POP3 and IMAP, where fetchmail
              will attempt to upgrade to TLSv1 or newer.

              Recognized values for --sslproto are given below. You should
              normally choose one of the auto-negotiating options, i. e.
              'tls1.2+' or 'auto' or one of the other options ending in a plus
              (+) character.  Note that depending on OpenSSL library version
              and configuration, some options cause run-time errors because
              the requested SSL or TLS versions are not supported by the
              particular installed OpenSSL library.

              'TLS1.2+'
                     (recommended). Since v6.4.0. Require TLS. Auto-negotiate
                     TLSv1.2 or newer.

              'auto' (default). Since v6.4.0. Require TLS. Auto-negotiate
                     TLSv1 or newer, disable SSLv3 downgrade.  (fetchmail
                     6.3.26 and older have auto-negotiated all protocols that
                     their OpenSSL library supported, including the broken
                     SSLv3).

              '', the empty string
                     Disable STARTTLS. If --ssl is given for the same server,
                     log an error and pretend that 'auto' had been used
                     instead.

              'SSL23'
                     see 'auto'.

              'SSL3' Require SSLv3 exactly. SSLv3 is broken, not supported on
                     all systems, avoid it if possible.  This will make
                     fetchmail negotiate SSLv3 only, and is the only way
                     besides 'SSL3+' to have fetchmail 6.4.0 or newer permit
                     SSLv3.

              'SSL3+'
                     same as 'auto', but permit SSLv3 as well. This is the
                     only way besides 'SSL3' to have fetchmail 6.4.0 or newer
                     permit SSLv3.

              'TLS1' Require TLSv1. This does not negotiate TLSv1.1 or newer,
                     and is discouraged. Replace by TLS1+ unless the latter
                     chokes your server.

              'TLS1+'
                     Since v6.4.0. See 'auto'.

              'TLS1.1'
                     Since v6.4.0. Require TLS v1.1 exactly.

              'TLS1.1+'
                     Since v6.4.0. Require TLS. Auto-negotiate TLSv1.1 or
                     newer.

              'TLS1.2'
                     Since v6.4.0. Require TLS v1.2 exactly.

              'TLS1.3'
                     Since v6.4.0. Require TLS v1.3 exactly.

              'TLS1.3+'
                     Since v6.4.0. Require TLS. Auto-negotiate TLSv1.3 or
                     newer.

              Unrecognized parameters
                     are treated the same as 'auto'.

              NOTE: you should hardly ever need to use anything other than ''
              (to force an unencrypted connection) or 'auto' (to enforce TLS).

       --sslcertck
              (Keyword: sslcertck, default enabled since v6.4.0)
              --sslcertck causes fetchmail to require that SSL/TLS be used and
              disconnect unless it can successfully negotiate SSL or TLS, or
              if it cannot successfully verify and validate the certificate
              and follow it to a trust anchor (or trusted root certificate).
              The trust anchors are given as a set of local trusted
              certificates (see the sslcertfile and sslcertpath options). If
              the server certificate cannot be obtained or is not signed by
              one of the trusted ones (directly or indirectly), fetchmail will
              disconnect, regardless of the sslfingerprint option.

       --nosslcertck
              (Keyword: no sslcertck, only in v6.4.X)
              The opposite of --sslcertck, this is a discouraged option. It
              permits fetchmail to continue connecting even if the server
              certificate failed the verification checks.  Should only be used
              together with --sslfingerprint.

       --sslcertfile <file>
              (Keyword: sslcertfile, since v6.3.17)
              Sets the file fetchmail uses to look up local certificates.  The
              default is empty.  This can be given in addition to
              --sslcertpath below, and certificates specified in --sslcertfile
              will be processed before those in --sslcertpath.  The option can
              be used in addition to --sslcertpath.

              The file is a text file. It contains the concatenation of
              trusted CA certificates in PEM format.

              Note that using this option will suppress loading the default
              SSL trusted CA certificates file unless you set the environment
              variable FETCHMAIL_INCLUDE_DEFAULT_X509_CA_CERTS to a non-empty
              value.

       --sslcertpath <directory>
              (Keyword: sslcertpath)
              Sets the directory fetchmail uses to look up local certificates.
              The default is your OpenSSL default directory. The directory
              must be hashed the way OpenSSL expects it - every time you add
              or modify a certificate in the directory, you need to use the
              c_rehash tool (which comes with OpenSSL in the tools/ sub-
              directory). Also, after OpenSSL upgrades, you may need to run
              c_rehash.

              This can be given in addition to --sslcertfile above, which see
              for precedence rules.

              Note that using this option will suppress adding the default SSL
              trusted CA certificates directory unless you set the environment
              variable FETCHMAIL_INCLUDE_DEFAULT_X509_CA_CERTS to a non-empty
              value.

       --sslcommonname <common name>
              (Keyword: sslcommonname; since v6.3.9)
              Use of this option is discouraged. Before using it, contact the
              administrator of your upstream server and ask for a proper SSL
              certificate to be used. If that cannot be attained, this option
              can be used to specify the name (CommonName) that fetchmail
              expects on the server certificate.  A correctly configured
              server will have this set to the host name by which it is
              reached, and by default fetchmail will expect as much. Use this
              option when the CommonName is set to some other value, to avoid
              the "Server CommonName mismatch" warning, and only if the
              upstream server's operator cannot be made to use proper
              certificates.

       --sslfingerprint <fingerprint>
              (Keyword: sslfingerprint)
              Specify the fingerprint of the server key (an MD5 hash of the
              key) in hexadecimal notation with colons separating groups of
              two digits. The letter hex digits must be in upper case. This is
              the format that fetchmail uses to report the fingerprint when an
              SSL connection is established. When this is specified, fetchmail
              will compare the server key fingerprint with the given one, and
              the connection will fail if they do not match, regardless of the
              sslcertck setting. The connection will also fail if fetchmail
              cannot obtain an SSL certificate from the server.  This can be
              used to prevent man-in-the-middle attacks, but the finger print
              from the server must be obtained or verified over a secure
              channel, and certainly not over the same Internet connection
              that fetchmail would use.

              Using this option will prevent printing certificate verification
              errors as long as --nosslcertck is in effect.

              To obtain the fingerprint of a certificate stored in the file
              cert.pem, try:

                   openssl x509 -in cert.pem -noout -md5 -fingerprint

              For details, see x509(1ssl).

   Delivery Control Options
       -S <hosts> | --smtphost <hosts>
              (Keyword: smtp[host])
              Specify a hunt list of hosts to forward mail to (one or more
              host names, comma-separated). Hosts are tried in list order; the
              first one that is up becomes the forwarding target for the
              current run.  If this option is not specified, 'localhost' is
              used as the default.  Each host name may have a port number
              following the host name.  The port number is separated from the
              host name by a slash; the default port is "smtp".  If you
              specify an absolute path name (beginning with a /), it will be
              interpreted as the name of a UNIX socket accepting LMTP
              connections (such as is supported by the Cyrus IMAP daemon)
              Example:

                   --smtphost server1,server2/2525,server3,/var/imap/socket/lmtp

              This option can be used with ODMR, and will make fetchmail a
              relay between the ODMR server and SMTP or LMTP receiver.

              WARNING: if you use address numeric IP addresses here, be sure
              to use --smtpaddress or --smtpname (either of which see) with a
              valid SMTP address literal!

       --fetchdomains <hosts>
              (Keyword: fetchdomains)
              In ETRN or ODMR mode, this option specifies the list of domains
              the server should ship mail for once the connection is turned
              around.  The default is the FQDN of the machine running
              fetchmail.

       -D <domain> | --smtpaddress <domain>
              (Keyword: smtpaddress)
              Specify the domain to be appended to addresses in RCPT TO lines
              shipped to SMTP. When this is not specified, the name of the
              SMTP server (as specified by --smtphost) is used for SMTP/LMTP
              and 'localhost' is used for UNIX socket/BSMTP.

              NOTE: if you intend to use numeric addresses, or so-called
              address literals per the SMTP standard, write them in proper
              SMTP syntax, for instance --smtpaddress "[192.0.2.6]" or
              --smtpaddress "[IPv6:2001:DB8::6]".

       --smtpname <user@domain>
              (Keyword: smtpname)
              Specify the domain and user to be put in RCPT TO lines shipped
              to SMTP.  The default user is the current local user. Please
              also see the NOTE about --smtpaddress and address literals
              above.

       -Z <nnn> | --antispam <nnn[, nnn]...>
              (Keyword: antispam)
              Specifies the list of numeric SMTP errors that are to be
              interpreted as a spam-block response from the listener.  A value
              of -1 disables this option.  For the command-line option, the
              list values should be comma-separated.  Note that the antispam
              values only apply to "MAIL FROM" responses in the SMTP/LMTP
              dialogue, but several MTAs (Postfix in its default
              configuration, qmail) defer the anti-spam response code until
              after the RCPT TO. --antispam does not work in these
              circumstances.  Also see --softbounce (default) and its inverse.

       -m <command> | --mda <command>
              (Keyword: mda)
              This option lets fetchmail use a Message or Local Delivery Agent
              (MDA or LDA) directly, rather than forward via SMTP or LMTP.

              To avoid losing mail, use this option only with MDAs like
              maildrop or MTAs like sendmail that exit with a nonzero status
              on disk-full and other delivery errors; the nonzero status tells
              fetchmail that delivery failed and prevents the message from
              being deleted on the server.

              If fetchmail is running as root, it sets its user id while
              delivering mail through an MDA as follows:  First, the
              FETCHMAILUSER, LOGNAME, and USER environment variables are
              checked in this order. The value of the first variable from his
              list that is defined (even if it is empty!) is looked up in the
              system user database. If none of the variables is defined,
              fetchmail will use the real user id it was started with. If one
              of the variables was defined, but the user stated there is not
              found, fetchmail continues running as root, without checking
              remaining variables on the list.  Practically, this means that
              if you run fetchmail as root (not recommended), it is most
              useful to define the FETCHMAILUSER environment variable to set
              the user that the MDA should run as. Some MDAs (such as
              maildrop) are designed to be setuid root and setuid to the
              recipient's user id, so you do not lose functionality this way
              even when running fetchmail as unprivileged user.  Check the
              MDA's manual for details.

              Some possible MDAs are "/usr/sbin/sendmail -i -f %F -- %T"
              (Note: some several older or vendor sendmail versions mistake --
              for an address, rather than an indicator to mark the end of the
              option arguments), "/usr/bin/deliver" and "/usr/bin/maildrop -d
              %T".  Local delivery addresses will be inserted into the MDA
              command wherever you place a %T; the mail message's From address
              will be inserted where you place an %F.

              Do NOT enclose the %F or %T string in single quotes!  For both
              %T and %F, fetchmail encloses the addresses in single quotes
              ('), after removing any single quotes they may contain, before
              the MDA command is passed to the shell.

              Do NOT use an MDA invocation that dispatches on the contents of
              To/Cc/Bcc, like "sendmail -i -t" or "qmail-inject", it will
              create mail loops and bring the just wrath of many postmasters
              down upon your head.  This is one of the most frequent
              configuration errors!

              Also, do not try to combine multidrop mode with an MDA such as
              maildrop that can only accept one address, unless your upstream
              stores one copy of the message per recipient and transports the
              envelope recipient in a header; you will lose mail.

              The well-known procmail(1) package is very hard to configure
              properly, it has a very nasty "fall through to the next rule"
              behavior on delivery errors (even temporary ones, such as out of
              disk space if another user's mail daemon copies the mailbox
              around to purge old messages), so your mail will end up in the
              wrong mailbox sooner or later. The proper procmail configuration
              is outside the scope of this document. Using maildrop(1) is
              usually much easier, and many users find the filter syntax used
              by maildrop easier to understand.

              Finally, we strongly advise that you do not use qmail-inject.
              The command line interface is non-standard without providing
              benefits for typical use, and fetchmail makes no attempts to
              accommodate qmail-inject's deviations from the standard. Some of
              qmail-inject's command-line and environment options are actually
              dangerous and can cause broken threads, non-detected duplicate
              messages and forwarding loops.


       --lmtp (Keyword: lmtp)
              Cause delivery via LMTP (Local Mail Transfer Protocol).  A
              service host and port must be explicitly specified on each host
              in the smtphost hunt list (see above) if this option is
              selected; the default port 25 will (in accordance with RFC 2033)
              not be accepted.

       --bsmtp <filename>
              (Keyword: bsmtp)
              Append fetched mail to a BSMTP file.  This simply contains the
              SMTP commands that would normally be generated by fetchmail when
              passing mail to an SMTP listener daemon.

              An argument of '-' causes the SMTP batch to be written to
              standard output, which is of limited use: this only makes sense
              for debugging, because fetchmail's regular output is
              interspersed on the same channel, so this is not suitable for
              mail delivery. This special mode may be removed in a later
              release.

              Note that fetchmail's reconstruction of MAIL FROM and RCPT TO
              lines is not guaranteed correct; the caveats discussed under THE
              USE AND ABUSE OF MULTIDROP MAILBOXES below apply.  This mode has
              precedence before --mda and SMTP/LMTP.

       --bad-header {reject|accept}
              (Keyword: bad-header; since v6.3.15)
              Specify how fetchmail is supposed to treat messages with bad
              headers, i.e., headers with bad syntax. Traditionally, fetchmail
              has rejected such messages, but some distributors modified
              fetchmail to accept them. You can now configure fetchmail's
              behaviour per server.


   Resource Limit Control Options
       -l <maxbytes> | --limit <maxbytes>
              (Keyword: limit)
              Takes a maximum octet size argument, where 0 is the default and
              also the special value designating "no limit".  If nonzero,
              messages larger than this size will not be fetched and will be
              left on the server (in foreground sessions, the progress
              messages will note that they are "oversized").  If the fetch
              protocol permits (in particular, under IMAP or POP3 without the
              fetchall option) the message will not be marked seen.

              An explicit --limit of 0 overrides any limits set in your run
              control file. This option is intended for those needing to
              strictly control fetch time due to expensive and variable phone
              rates.

              Combined with --limitflush, it can be used to delete oversized
              messages waiting on a server.  In daemon mode, oversize
              notifications are mailed to the calling user (see the --warnings
              option). This option does not work with ETRN or ODMR.

       -w <interval> | --warnings <interval>
              (Keyword: warnings)
              Takes an interval in seconds.  When you call fetchmail with a
              'limit' option in daemon mode, this controls the interval at
              which warnings about oversized messages are mailed to the
              calling user (or the user specified by the 'postmaster' option).
              One such notification is always mailed at the end of the first
              poll that the oversized message is detected.  Thereafter, re-
              notification is suppressed until after the warning interval
              elapses (it will take place at the end of the first following
              poll).

       -b <count> | --batchlimit <count>
              (Keyword: batchlimit)
              Specify the maximum number of messages that will be shipped to
              an SMTP listener before the connection is deliberately torn down
              and rebuilt (defaults to 0, meaning no limit).  An explicit
              --batchlimit of 0 overrides any limits set in your run control
              file.  While sendmail(8) normally initiates delivery of a
              message immediately after receiving the message terminator, some
              SMTP listeners are not so prompt.  MTAs like smail(8) may wait
              till the delivery socket is shut down to deliver.  This may
              produce annoying delays when fetchmail is processing very large
              batches.  Setting the batch limit to some nonzero size will
              prevent these delays.  This option does not work with ETRN or
              ODMR.

       -B <number> | --fetchlimit <number>
              (Keyword: fetchlimit)
              Limit the number of messages accepted from a given server in a
              single poll.  By default there is no limit. An explicit
              --fetchlimit of 0 overrides any limits set in your run control
              file.  This option does not work with ETRN or ODMR.

       --fetchsizelimit <number>
              (Keyword: fetchsizelimit)
              Limit the number of sizes of messages accepted from a given
              server in a single transaction.  This option is useful in
              reducing the delay in downloading the first mail when there are
              too many mails in the mailbox.  By default, the limit is 100.
              If set to 0, sizes of all messages are downloaded at the start.
              This option does not work with ETRN or ODMR.  For POP3, the only
              valid non-zero value is 1.

       --fastuidl <number>
              (Keyword: fastuidl)
              Do a binary instead of linear search for the first unseen UID.
              Binary search avoids downloading the UIDs of all mails. This
              saves time (especially in daemon mode) where downloading the
              same set of UIDs in each poll is a waste of bandwidth. The
              number 'n' indicates how rarely a linear search should be done.
              In daemon mode, linear search is used once followed by binary
              searches in 'n-1' polls if 'n' is greater than 1; binary search
              is always used if 'n' is 1; linear search is always used if 'n'
              is 0. In non-daemon mode, binary search is used if 'n' is 1;
              otherwise linear search is used. The default value of 'n' is 4.
              This option works with POP3 only.

       -e <count> | --expunge <count>
              (Keyword: expunge)
              Arrange for deletions to be made final after a given number of
              messages.  Under POP2 or POP3, fetchmail cannot make deletions
              final without sending QUIT and ending the session -- with this
              option on, fetchmail will break a long mail retrieval session
              into multiple sub-sessions, sending QUIT after each sub-session.
              This is a good defense against line drops on POP3 servers.
              Under IMAP, fetchmail normally issues an EXPUNGE command after
              each deletion in order to force the deletion to be done
              immediately.  This is safest when your connection to the server
              is flaky and expensive, as it avoids re-sending duplicate mail
              after a line hit.  However, on large mailboxes the overhead of
              re-indexing after every message can slam the server pretty hard,
              so if your connection is reliable it is good to do expunges less
              frequently.  Also note that some servers enforce a delay of a
              few seconds after each quit, so fetchmail may not be able to get
              back in immediately after an expunge -- you may see "lock busy"
              errors if this happens. If you specify this option to an integer
              N, it tells fetchmail to only issue expunges on every Nth
              delete.  An argument of zero suppresses expunges entirely (so no
              expunges at all will be done until the end of run).  This option
              does not work with ETRN or ODMR.


   Authentication Options
       -u <name> | --user <name> | --username <name>
              (Keyword: user[name])
              Specifies the user identification to be used when logging in to
              the mail server.  The appropriate user identification is both
              server and user-dependent.  The default is your login name on
              the client machine that is running fetchmail.  See USER
              AUTHENTICATION below for a complete description.

       -I <specification> | --interface <specification>
              (Keyword: interface)
              Require that a specific interface device be up and have a
              specific local or remote IPv4 (IPv6 is not supported by this
              option yet) address (or range) before polling.  Frequently
              fetchmail is used over a transient point-to-point TCP/IP link
              established directly to a mail server via SLIP or PPP.  That is
              a relatively secure channel.  But when other TCP/IP routes to
              the mail server exist (e.g., when the link is connected to an
              alternate ISP), your username and password may be vulnerable to
              snooping (especially when daemon mode automatically polls for
              mail, shipping a clear password over the net at predictable
              intervals).  The --interface option may be used to prevent this.
              When the specified link is not up or is not connected to a
              matching IP address, polling will be skipped.  The format is:

                   interface/iii.iii.iii.iii[/mmm.mmm.mmm.mmm]

              The field before the first slash is the interface name (i.e.,
              sl0, ppp0 etc.).  The field before the second slash is the
              acceptable IP address.  The field after the second slash is a
              mask which specifies a range of IP addresses to accept.  If no
              mask is present 255.255.255.255 is assumed (i.e., an exact
              match).  This option is currently only supported under Linux and
              FreeBSD. Please see the monitor section for below for FreeBSD
              specific information.

              Note that this option may be removed from a future fetchmail
              version.

       -M <interface> | --monitor <interface>
              (Keyword: monitor)
              Daemon mode can cause transient links which are automatically
              taken down after a period of inactivity (e.g., PPP links) to
              remain up indefinitely.  This option identifies a system TCP/IP
              interface to be monitored for activity.  After each poll
              interval, if the link is up but no other activity has occurred
              on the link, then the poll will be skipped.  However, when
              fetchmail is woken up by a signal, the monitor check is skipped
              and the poll goes through unconditionally.  This option is
              currently only supported under Linux and FreeBSD.  For the
              monitor and interface options to work for non root users under
              FreeBSD, the fetchmail binary must be installed setgid kmem.
              This would be a security hole, but fetchmail runs with the
              effective GID set to that of the kmem group only when interface
              data is being collected.

              Note that this option may be removed from a future fetchmail
              version.

       --auth <type>
              (Keyword: auth[enticate])
              This option permits you to specify an authentication type (see
              USER AUTHENTICATION below for details).  The possible values are
              any, password, kerberos_v5, kerberos (or, for excruciating
              exactness, kerberos_v4), gssapi, cram-md5, otp, ntlm, msn (only
              for POP3), external (only IMAP) and ssh.  When any (the default)
              is specified, fetchmail tries first methods that do not require
              a password (EXTERNAL, GSSAPI, KERBEROS IV, KERBEROS 5); then it
              looks for methods that mask your password (CRAM-MD5, NTLM, X-OTP
              - note that MSN is only supported for POP3, but not auto-
              probed); and only if the server does not support any of those
              will it ship your password unencrypted.  Other values may be
              used to force various authentication methods: ssh suppresses
              authentication and is thus useful for IMAP PREAUTH (if you are
              using a secure --plugin, for instance, a properly configured
              ssh, you may also need to set --sslproto '' or, in the rcfile,
              sslproto '', in order to avoid fetchmail negotiating STARTTLS
              over SSH).  external suppresses authentication and is thus
              useful for IMAP EXTERNAL.  Any value other than password,
              cram-md5, ntlm, msn or otp suppresses fetchmail's normal inquiry
              for a password.  Specify ssh when you are using an end-to-end
              secure connection such as an ssh tunnel (in this case you may
              also want to specify --sslproto '', which see); specify external
              when you use TLS with client authentication and specify gssapi
              or kerberos_v4 if you are using a protocol variant that employs
              GSSAPI or K4.  Choosing KPOP protocol automatically selects
              Kerberos authentication.  This option does not work with ETRN.
              GSSAPI service names are in line with RFC-2743 and IANA
              registrations, see Generic Security Service Application Program
              Interface (GSSAPI)/Kerberos/Simple Authentication and Security
              Layer (SASL) Service Names
              <https://www.iana.org/assignments/gssapi-service-names/>.

   Miscellaneous Options
       -f <pathname> | --fetchmailrc <pathname>
              Specify a non-default name for the ~/.fetchmailrc run control
              file.  The pathname argument must be either "-" (a single dash,
              meaning to read the configuration from standard input) or a
              filename.  Unless the --version option is also on, a named file
              argument must have permissions no more open than 0700
              (u=rwx,g=,o=) or else be /dev/null.

       -i <pathname> | --idfile <pathname>
              (Keyword: idfile)
              Specify an alternate name for the .fetchids file used to save
              message UIDs. NOTE: since fetchmail 6.3.0, write access to the
              directory containing the idfile is required, as fetchmail writes
              a temporary file and renames it into the place of the real
              idfile only if the temporary file has been written successfully.
              This avoids the truncation of idfiles when running out of disk
              space.

       --pidfile <pathname>
              (Keyword: pidfile; since fetchmail v6.3.4)
              Override the default location of the PID file that is used as a
              lock file.  Default: see "ENVIRONMENT" below. Note that many
              places in the code and documentation, the term "lock file" is
              used.  This file contains the process ID of the running
              fetchmail on the first line and potentially the daemon interval
              on a second line.

       -n | --norewrite
              (Keyword: no rewrite)
              Normally, fetchmail edits RFC-822 address headers (To, From, Cc,
              Bcc, and Reply-To) in fetched mail so that any mail IDs local to
              the server are expanded to full addresses (@ and the mail server
              host name are appended).  This enables replies on the client to
              get addressed correctly (otherwise your mailer might think they
              should be addressed to local users on the client machine!).
              This option disables the rewrite.  (This option is provided to
              pacify people who are paranoid about having an MTA edit mail
              headers and want to know they can prevent it, but it is
              generally not a good idea to actually turn off rewrite.)  When
              using ETRN or ODMR, the rewrite option is ineffective.

       -E <line> | --envelope <line>
              (Keyword: envelope; Multidrop only)
              In the configuration file, an enhanced syntax is used:
              envelope [<count>] <line>

              This option changes the header fetchmail assumes will carry a
              copy of the mail's envelope address.  Normally this is
              'X-Envelope-To'.  Other typically found headers to carry
              envelope information are 'X-Original-To' and 'Delivered-To'.
              Now, since these headers are not standardized, practice varies.
              See the discussion of multidrop address handling below.  As a
              special case, 'envelope "Received"' enables parsing of sendmail-
              style Received lines.  This is the default, but discouraged
              because it is not fully reliable.

              Note that fetchmail expects the Received-line to be in a
              specific format: It must contain "by host for address", where
              host must match one of the mail server names that fetchmail
              recognizes for the account in question.

              The optional count argument (only available in the configuration
              file) determines how many header lines of this kind are skipped.
              A count of 1 means: skip the first, take the second. A count of
              2 means: skip the first and second, take the third, and so on.

       -Q <prefix> | --qvirtual <prefix>
              (Keyword: qvirtual; Multidrop only)
              The string prefix assigned to this option will be removed from
              the user name found in the header specified with the envelope
              option (before doing multidrop name mapping or localdomain
              checking, if either is applicable). This option is useful if you
              are using fetchmail to collect the mail for an entire domain and
              your ISP (or your mail redirection provider) is using qmail.
              One of the basic features of qmail is the Delivered-To: message
              header.  Whenever qmail delivers a message to a local mailbox it
              puts the username and host name of the envelope recipient on
              this line.  The major reason for this is to prevent mail loops.
              To set up qmail to batch mail for a disconnected site the ISP-
              mailhost will have normally put that site in its 'Virtualhosts'
              control file so it will add a prefix to all mail addresses for
              this site. This results in mail sent to
              'username@userhost.userdom.dom.com' having a Delivered-To: line
              of the form:

              Delivered-To: mbox-userstr-username@userhost.example.com

              The ISP can make the 'mbox-userstr-' prefix anything they choose
              but a string matching the user host name is likely.  By using
              the option 'envelope Delivered-To:' you can make fetchmail
              reliably identify the original envelope recipient, but you have
              to strip the 'mbox-userstr-' prefix to deliver to the correct
              user.  This is what this option is for.

       --configdump
              Parse the ~/.fetchmailrc file, interpret any command-line
              options specified, and dump a configuration report to standard
              output.  The configuration report is a data structure assignment
              in the language Python.  This option is meant to be used with an
              interactive ~/.fetchmailrc editor like fetchmailconf, written in
              Python.

       -y | --yydebug
              Enables parser debugging, this option is meant to be used by
              developers only.


   Removed Options
       -T | --netsec
              Removed before version 6.3.0, the required underlying inet6_apps
              library had been discontinued and is no longer available.


USER AUTHENTICATION AND ENCRYPTION
       All modes except ETRN require authentication of the client to the
       server.  Normal user authentication in fetchmail is very much like the
       authentication mechanism of ftp(1).  The correct user-id and password
       depend upon the underlying security system at the mail server.

       If the mail server is a Unix machine on which you have an ordinary user
       account, your regular login name and password are used with fetchmail.
       If you use the same login name on both the server and the client
       machines, you needn't worry about specifying a user-id with the -u
       option -- the default behavior is to use your login name on the client
       machine as the user-id on the server machine.  If you use a different
       login name on the server machine, specify that login name with the -u
       option.  E.g., if your login name is 'jsmith' on a machine named
       'mailgrunt', you would start fetchmail as follows:

              fetchmail -u jsmith mailgrunt

       The default behavior of fetchmail is to prompt you for your mail server
       password before the connection is established.  This is the safest way
       to use fetchmail and ensures that your password will not be
       compromised.  You may also specify your password in your ~/.fetchmailrc
       file.  This is convenient when using fetchmail in daemon mode or with
       scripts.


   Using netrc files
       If you do not specify a password, and fetchmail cannot extract one from
       your ~/.fetchmailrc file, it will look for a ~/.netrc file in your home
       directory before requesting one interactively; if an entry matching the
       mail server is found in that file, the password will be used.
       Fetchmail first looks for a match on poll name; if it finds none, it
       checks for a match on via name.  See the ftp(1) man page for details of
       the syntax of the ~/.netrc file.  To show a practical example, a .netrc
       might look like this:

              machine hermes.example.org
              login joe
              password topsecret

       You can repeat this block with different user information if you need
       to provide more than one password.

       This feature may allow you to avoid duplicating password information in
       more than one file.

       On mail servers that do not provide ordinary user accounts, your user-
       id and password are usually assigned by the server administrator when
       you apply for a mailbox on the server.  Contact your server
       administrator if you do not know the correct user-id and password for
       your mailbox account.


   Secure Socket Layers (SSL) and Transport Layer Security (TLS)
       All retrieval protocols can use SSL or TLS wrapping for the transport.
       Additionally, POP3 and IMAP retrieval can also negotiate SSL/TLS by
       means of STARTTLS (or STLS).

       You can access TLS-encrypted services by specifying the options
       starting with --ssl, such as --ssl, --sslproto, --sslcertck, and
       others.  You can also do this using the corresponding user options in
       the .fetchmailrc file.  Some services, such as POP3 and IMAP, have
       different well known ports defined for the SSL encrypted services.  The
       encrypted ports will be selected automatically when SSL is enabled and
       no explicit port is specified.   Also, the --sslcertck command line or
       sslcertck run control file option should be used to force strict
       certificate checking with older fetchmail versions - see below.

       If TLS or SSL is not configured, fetchmail will usually still try to
       use STARTTLS somewhat opportunistically. In practice, is it still
       mandatory because --sslcertck is a default setting and implicitly
       requires STARTTLS.

       STARTTLS can be enforced by using --sslproto auto and defeated by using
       --sslproto ''.  STARTTLS connections use the same port as the
       unencrypted version of the protocol and negotiate TLS via special
       command. The --sslcertck command line or sslcertck run control file
       option should be used to force strict certificate checking - see below.

       --sslcertck is recommended: When connecting to an SSL or TLS encrypted
       server, the server presents a certificate to the client for validation.
       The certificate is checked to verify that the common name in the
       certificate matches the name of the server being contacted and that the
       effective and expiration dates in the certificate indicate that it is
       currently valid.  If any of these checks fail, a warning message is
       printed, but the connection continues.  The server certificate does not
       need to be signed by any specific Certifying Authority and may be a
       "self-signed" certificate. If the --sslcertck command line option or
       sslcertck run control file option is used, fetchmail will instead abort
       if any of these checks fail, because it must assume that there is a
       man-in-the-middle attack in this scenario, hence fetchmail must not
       expose clear-text passwords. Use of the sslcertck or --sslcertck option
       is therefore advised; it has become the default in fetchmail 6.4.0.

       Some SSL encrypted servers may request a client side certificate.  A
       client side public SSL certificate and private SSL key may be
       specified.  If requested by the server, the client certificate is sent
       to the server for validation.  Some servers may require a valid client
       certificate and may refuse connections if a certificate is not provided
       or if the certificate is not valid.  Some servers may require client
       side certificates be signed by a recognized Certifying Authority.  The
       format for the key files and the certificate files is that required by
       the underlying SSL libraries (OpenSSL in the general case).

       A word of care about the use of SSL: While above mentioned setup with
       self-signed server certificates retrieved over the wires can protect
       you from a passive eavesdropper, it does not help against an active
       attacker. It is clearly an improvement over sending the passwords in
       clear, but you should be aware that a man-in-the-middle attack is
       trivially possible (in particular with tools such as dsniff
       <https://monkey.org/~dugsong/dsniff/>).  Use of strict certificate
       checking with a certification authority recognized by server and
       client, or perhaps of an SSH tunnel (see below for some examples) is
       preferable if you care seriously about the security of your mailbox and
       passwords.


POP3 VARIANTS
       Early versions of POP3 (RFC1081, RFC1225) supported a crude form of
       independent authentication using the .rhosts file on the mail server
       side.  Under this RPOP variant, a fixed per-user ID equivalent to a
       password was sent in clear over a link to a reserved port, with the
       command RPOP rather than PASS to alert the server that it should do
       special checking.  RPOP is supported by fetchmail (you can specify
       'protocol RPOP' to have the program send 'RPOP' rather than 'PASS') but
       its use is strongly discouraged, and support will be removed from a
       future fetchmail version.  This facility was vulnerable to spoofing and
       was withdrawn in RFC1460.

       RFC1460 introduced APOP authentication.  In this variant of POP3, you
       register an APOP password on your server host (on some servers, the
       program to do this is called popauth(8)).  You put the same password in
       your ~/.fetchmailrc file.  Each time fetchmail logs in, it sends an MD5
       hash of your password and the server greeting time to the server, which
       can verify it by checking its authorization database.

       Note that APOP is no longer considered resistant against man-in-the-
       middle attacks.


   RETR or TOP
       fetchmail makes some efforts to make the server believe messages had
       not been retrieved, by using the TOP command with a large number of
       lines when possible.  TOP is a command that retrieves the full header
       and a fetchmail-specified amount of body lines. It is optional and
       therefore not implemented by all servers, and some are known to
       implement it improperly. On many servers however, the RETR command
       which retrieves the full message with header and body, sets the "seen"
       flag (for instance, in a web interface), whereas the TOP command does
       not do that.

       fetchmail will always use the RETR command if "fetchall" is set.
       fetchmail will also use the RETR command if "keep" is set and "uidl" is
       unset.  Finally, fetchmail will use the RETR command on Maillennium
       POP3/PROXY servers (used by Comcast) to avoid a deliberate TOP
       misinterpretation in this server that causes message corruption.

       In all other cases, fetchmail will use the TOP command. This implies
       that in "keep" setups, "uidl" must be set if "TOP" is desired.

       Note that this description is true for the current version of
       fetchmail, but the behavior may change in future versions. In
       particular, fetchmail may prefer the RETR command because the TOP
       command causes much grief on some servers and is only optional.

ALTERNATE AUTHENTICATION FORMS/METHODS
       If your fetchmail was built with Kerberos support and you specify
       Kerberos authentication (either with --auth or the .fetchmailrc option
       authenticate kerberos_v4) it will try to get a Kerberos ticket from the
       mail server at the start of each query.  Note: if either the pollname
       or via name is 'hesiod', fetchmail will try to use Hesiod to look up
       the mail server.

       If you use POP3 or IMAP with GSSAPI authentication, fetchmail will
       expect the server to have RFC1731- or RFC1734-conforming GSSAPI
       capability, and will use it.  Currently this has only been tested over
       Kerberos 5, so you are expected to already have a ticket-granting
       ticket. You may pass a username different from your principal name
       using the standard --user command or by the .fetchmailrc option user.

       If your IMAP daemon returns the PREAUTH response in its greeting line,
       fetchmail will notice this and skip the normal authentication step.
       This can be useful, e.g., if you start imapd explicitly using ssh.  In
       this case you can declare the authentication value 'ssh' on that site
       entry to stop .fetchmail from asking you for a password when it starts
       up.

       If you use client authentication with TLS1 and your IMAP daemon returns
       the AUTH=EXTERNAL response, fetchmail will notice this and will use the
       authentication shortcut and will not send the passphrase. In this case
       you can declare the authentication value 'external'
        on that site to stop fetchmail from asking you for a password when it
       starts up.

       If you are using POP3, and the server issues a one-time-password
       challenge conforming to RFC1938, fetchmail will use your password as a
       pass phrase to generate the required response. This avoids sending
       secrets over the net unencrypted.

       Compuserve's RPA authentication is supported. If you compile in the
       support, fetchmail will try to perform an RPA pass-phrase
       authentication instead of sending over the password unencrypted if it
       detects "@compuserve.com" in the host name.

       If you are using IMAP, Microsoft's NTLM authentication (used by
       Microsoft Exchange) is supported. If you compile in the support,
       fetchmail will try to perform an NTLM authentication (instead of
       sending over the password unencrypted) whenever the server returns
       AUTH=NTLM in its capability response. Specify a user option value that
       looks like 'user@domain': the part to the left of the @ will be passed
       as the username and the part to the right as the NTLM domain.


   ESMTP AUTH
       fetchmail also supports authentication to the ESMTP server on the
       client side according to RFC 2554.  You can specify a name/password
       pair to be used with the keywords 'esmtpname' and 'esmtppassword'; the
       former defaults to the username of the calling user.


DAEMON MODE
   Introducing the daemon mode
       In daemon mode, fetchmail puts itself into the background and runs
       forever, querying each specified host and then sleeping for a given
       polling interval.

   Starting the daemon mode
       There are several ways to make fetchmail work in daemon mode. On the
       command line, --daemon <interval> or -d <interval> option runs
       fetchmail in daemon mode.  You must specify a numeric argument which is
       a polling interval (time to wait after completing a whole poll cycle
       with the last server and before starting the next poll cycle with the
       first server) in seconds.

       Example: simply invoking

              fetchmail -d 900

       will, therefore, poll all the hosts described in your ~/.fetchmailrc
       file (except those explicitly excluded with the 'skip' verb) a bit less
       often than once every 15 minutes (exactly: 15 minutes + time that the
       poll takes).

       It is also possible to set a polling interval in your ~/.fetchmailrc
       file by saying 'set daemon <interval>', where <interval> is an integer
       number of seconds.  If you do this, fetchmail will always start in
       daemon mode unless you override it with the command-line option
       --daemon 0 or -d0.

       Only one daemon process is permitted per user; in daemon mode,
       fetchmail sets up a per-user lock file to guarantee this.  (You can
       however cheat and set the FETCHMAILHOME environment variable to
       overcome this setting, but in that case, it is your responsibility to
       make sure you are not polling the same server with two processes at the
       same time.)

   Awakening the background daemon
       Normally, calling fetchmail with a daemon in the background sends a
       wake-up signal to the daemon and quits without output. The background
       daemon then starts its next poll cycle immediately.  The wake-up
       signal, SIGUSR1, can also be sent manually. The wake-up action also
       clears any 'wedged' flags indicating that connections have wedged due
       to failed authentication or multiple timeouts.

   Terminating the background daemon
       The option -q or --quit will kill a running daemon process instead of
       waking it up (if there is no such process, fetchmail will notify you).
       If the --quit option appears last on the command line, fetchmail will
       kill the running daemon process and then quit. Otherwise, fetchmail
       will first kill a running daemon process and then continue running with
       the other options.

   Useful options for daemon mode
       The -L <filename> or --logfile <filename> option (keyword: set logfile)
       is only effective when fetchmail is detached and in daemon mode. Note
       that the logfile must exist before fetchmail is run, you can use the
       touch(1) command with the filename as its sole argument to create it.
       This option allows you to redirect status messages into a specified
       logfile (follow the option with the logfile name).  The logfile is
       opened for append, so previous messages are not deleted.  This is
       primarily useful for debugging configurations. Note that fetchmail does
       not detect if the logfile is rotated, the logfile is only opened once
       when fetchmail starts. You need to restart fetchmail after rotating the
       logfile and before compressing it (if applicable).

       The --syslog option (keyword: set syslog) allows you to redirect status
       and error messages emitted to the syslog(3) system daemon if available.
       Messages are logged with an id of fetchmail, the facility LOG_MAIL, and
       priorities LOG_ERR, LOG_ALERT or LOG_INFO.  This option is intended for
       logging status and error messages which indicate the status of the
       daemon and the results while fetching mail from the server(s).  Error
       messages for command line options and parsing the .fetchmailrc file are
       still written to stderr, or to the specified log file.  The --nosyslog
       option turns off use of syslog(3), assuming it is turned on in the
       ~/.fetchmailrc file.  This option is overridden, in certain situations,
       by --logfile (which see).

       The -N or --nodetach option suppresses backgrounding and detachment of
       the daemon process from its control terminal.  This is useful for
       debugging or when fetchmail runs as the child of a supervisor process
       such as init(8) or Gerrit Pape's runit(8).  Note that this also causes
       the logfile option to be ignored.

       Note that while running in daemon mode polling a POP2 or IMAP2bis
       server, transient errors (such as DNS failures or sendmail delivery
       refusals) may force the fetchall option on for the duration of the next
       polling cycle.  This is a robustness feature.  It means that if a
       message is fetched (and thus marked seen by the mail server) but not
       delivered locally due to some transient error, it will be re-fetched
       during the next poll cycle.  (The IMAP logic does not delete messages
       until they are delivered, so this problem does not arise.)

       If you touch or change the ~/.fetchmailrc file while fetchmail is
       running in daemon mode, this will be detected at the beginning of the
       next poll cycle.  When a changed ~/.fetchmailrc is detected, fetchmail
       rereads it and restarts from scratch (using exec(2); no state
       information is retained in the new instance).  Note that if fetchmail
       needs to query for passwords, of that if you break the ~/.fetchmailrc
       file's syntax, the new instance will softly and silently vanish away on
       startup.


ADMINISTRATIVE OPTIONS
       The --postmaster <name> option (keyword: set postmaster) specifies the
       last-resort username to which multidrop mail is to be forwarded if no
       matching local recipient can be found. It is also used as destination
       of undeliverable mail if the 'bouncemail' global option is off and
       additionally for spam-blocked mail if the 'bouncemail' global option is
       off and the 'spambounce' global option is on. This option defaults to
       the user who invoked fetchmail.  If the invoking user is root, then the
       default of this option is the user 'postmaster'.  Setting postmaster to
       the empty string causes such mail as described above to be discarded -
       this however is usually a bad idea.  See also the description of the
       'FETCHMAILUSER' environment variable in the ENVIRONMENT section below.

       The --nobounce behaves like the "set no bouncemail" global option,
       which see.

       The --invisible option (keyword: set invisible) tries to make fetchmail
       invisible.  Normally, fetchmail behaves like any other MTA would -- it
       generates a Received header into each message describing its place in
       the chain of transmission, and tells the MTA it forwards to that the
       mail came from the machine fetchmail itself is running on.  If the
       invisible option is on, the Received header is suppressed and fetchmail
       tries to spoof the MTA it forwards to into thinking it came directly
       from the mail server host.

       The --showdots option (keyword: set showdots) forces fetchmail to show
       progress dots even if the output goes to a file or fetchmail is not in
       verbose mode.  Fetchmail shows the dots by default when run in
       --verbose mode and output goes to console. This option is ignored in
       --silent mode.

       By specifying the --tracepolls option, you can ask fetchmail to add
       information to the Received header on the form "polling {label} account
       {user}", where {label} is the account label (from the specified rcfile,
       normally ~/.fetchmailrc) and {user} is the username which is used to
       log on to the mail server. This header can be used to make filtering
       email where no useful header information is available and you want mail
       from different accounts sorted into different mailboxes (this could,
       for example, occur if you have an account on the same server running a
       mailing list, and are subscribed to the list using that account). The
       default is not adding any such header.  In .fetchmailrc, this is called
       'tracepolls'.


RETRIEVAL FAILURE MODES
       The protocols fetchmail uses to talk to mail servers are next to
       bulletproof.  In normal operation forwarding to port 25, no message is
       ever deleted (or even marked for deletion) on the host until the SMTP
       listener on the client side has acknowledged to fetchmail that the
       message has been either accepted for delivery or rejected due to a spam
       block.

       When forwarding to an MDA, however, there is more possibility of error.
       Some MDAs are 'safe' and reliably return a nonzero status on any
       delivery error, even one due to temporary resource limits.  The
       maildrop(1) program is like this; so are most programs designed as mail
       transport agents, such as sendmail(1), including the sendmail wrapper
       of Postfix and exim(1).  These programs give back a reliable positive
       acknowledgement and can be used with the mda option with no risk of
       mail loss.  Unsafe MDAs, though, may return 0 even on delivery failure.
       If this happens, you will lose mail.

       The normal mode of fetchmail is to try to download only 'new' messages,
       leaving untouched (and undeleted) messages you have already read
       directly on the server (or fetched with a previous fetchmail --keep).
       But you may find that messages you have already read on the server are
       being fetched (and deleted) even when you do not specify --all.  There
       are several reasons this can happen.

       One could be that you are using POP2.  The POP2 protocol includes no
       representation of 'new' or 'old' state in messages, so fetchmail must
       treat all messages as new all the time.  But POP2 is obsolete, so this
       is unlikely.

       A potential POP3 problem might be servers that insert messages in the
       middle of mailboxes (some VMS implementations of mail are rumored to do
       this).  The fetchmail code assumes that new messages are appended to
       the end of the mailbox; when this is not true it may treat some old
       messages as new and vice versa.  Using UIDL whilst setting fastuidl 0
       might fix this, otherwise, consider switching to IMAP.

       Yet another POP3 problem is that if they cannot make temporary files in
       the user's home directory, some POP3 servers will hand back an
       undocumented response that causes fetchmail to spuriously report "No
       mail".

       The IMAP code uses the presence or absence of the server flag \Seen to
       decide whether or not a message is new.  This is not the right thing to
       do, fetchmail should check the UIDVALIDITY and use UID, but it does not
       do that yet. Under Unix, it counts on your IMAP server to notice the
       BSD-style Status flags set by mail user agents and set the \Seen flag
       from them when appropriate.  All Unix IMAP servers we know of do this,
       though it is not specified by the IMAP RFCs.  If you ever trip over a
       server that does not, the symptom will be that messages you have
       already read on your host will look new to the server.  In this
       (unlikely) case, only messages you fetched with fetchmail --keep will
       be both undeleted and marked old.

       In ETRN and ODMR modes, fetchmail does not actually retrieve messages;
       instead, it asks the server's SMTP listener to start a queue flush to
       the client via SMTP.  Therefore it sends only undelivered messages.


SPAM FILTERING
       Many SMTP listeners allow administrators to set up 'spam filters' that
       block unsolicited email from specified domains.  A MAIL FROM or DATA
       line that triggers this feature will elicit an SMTP response which
       (unfortunately) varies according to the listener.

       Newer versions of sendmail return an error code of 571.

       According to RFC2821, the correct thing to return in this situation is
       550 "Requested action not taken: mailbox unavailable" (the draft adds
       "[E.g., mailbox not found, no access, or command rejected for policy
       reasons].").

       Older versions of the exim MTA return 501 "Syntax error in parameters
       or arguments".

       The postfix MTA runs 554 as an antispam response.

       Zmailer may reject code with a 500 response (followed by an enhanced
       status code that contains more information).

       Return codes which fetchmail treats as antispam responses and discards
       the message can be set with the 'antispam' option.  This is one of the
       only three circumstance under which fetchmail ever discards mail (the
       others are the 552 and 553 errors described below, and the suppression
       of multi-dropped messages with a message-ID already seen).

       If fetchmail is fetching from an IMAP server, the antispam response
       will be detected and the message rejected immediately after the headers
       have been fetched, without reading the message body.  Thus, you will
       not pay for downloading spam message bodies.

       By default, the list of antispam responses is empty.

       If the spambounce global option is on, mail that is spam-blocked
       triggers an RFC1892/RFC1894 bounce message informing the originator
       that we do not accept mail from it. See also BUGS.


SMTP/ESMTP ERROR HANDLING
       Besides the spam-blocking described above, fetchmail takes special
       actions -- that may be modified by the --softbounce option -- on the
       following SMTP/ESMTP error response codes

       452 (insufficient system storage)
            Leave the message in the server mailbox for later retrieval.

       552 (message exceeds fixed maximum message size)
            Delete the message from the server.  Send bounce-mail to the
            originator.

       553 (invalid sending domain)
            Delete the message from the server.  Do not even try to send
            bounce-mail to the originator.

       Other errors greater or equal to 500 trigger bounce mail back to the
       originator, unless suppressed by --softbounce. See also BUGS.


THE RUN CONTROL FILE
       The preferred way to set up fetchmail is to write a .fetchmailrc file
       in your home directory (you may do this directly, with a text editor,
       or indirectly via fetchmailconf).  When there is a conflict between the
       command-line arguments and the arguments in this file, the command-line
       arguments take precedence.

       To protect the security of your passwords, your ~/.fetchmailrc may not
       normally have more than 0700 (u=rwx,g=,o=) permissions; fetchmail will
       complain and exit otherwise (this check is suppressed when --version is
       on).

       You may read the .fetchmailrc file as a list of commands to be executed
       when fetchmail is called with no arguments.

   Run Control Syntax
       Comments begin with a '#' and extend through the end of the line.
       Otherwise the file consists of a series of server entries or global
       option statements in a free-format, token-oriented syntax.

       There are four kinds of tokens: grammar keywords, numbers (i.e.,
       decimal digit sequences), unquoted strings, and quoted strings.  A
       quoted string is bounded by double quotes and may contain whitespace
       (and quoted digits are treated as a string).  Note that quoted strings
       will also contain line feed characters if they run across two or more
       lines, unless you use a backslash to join lines (see below).  An
       unquoted string is any whitespace-delimited token that is neither
       numeric, string quoted nor contains the special characters ',', ';',
       ':', or '='.

       Any amount of whitespace separates tokens in server entries, but is
       otherwise ignored. You may use backslash escape sequences (\n for LF,
       \t for HT, \b for BS, \r for CR, \nnn for decimal (where nnn cannot
       start with a 0), \0ooo for octal, and \xhh for hex) to embed non-
       printable characters or string delimiters in strings.  In quoted
       strings, a backslash at the very end of a line will cause the backslash
       itself and the line feed (LF or NL, new line) character to be ignored,
       so that you can wrap long strings. Without the backslash at the line
       end, the line feed character would become part of the string.

       Warning: while these resemble C-style escape sequences, they are not
       the same.  fetchmail only supports these eight styles. C supports more
       escape sequences that consist of backslash (\) and a single character,
       but does not support decimal codes and does not require the leading 0
       in octal notation.  Example: fetchmail interprets \233 the same as \xE9
       (Latin small letter e with acute), where C would interpret \233 as
       octal 0233 = \x9B (CSI, control sequence introducer).

       Each server entry consists of one of the keywords 'poll' or 'skip',
       followed by a server name, followed by server options, followed by any
       number of user (or username) descriptions, followed by user options.
       Note: the most common cause of syntax errors is mixing up user and
       server options or putting user options before the user descriptions.

       For backward compatibility, the word 'server' is a synonym for 'poll'.

       You can use the noise keywords 'and', 'with', 'has', 'wants', and
       'options' anywhere in an entry to make it resemble English.  They are
       ignored, but can make entries much easier to read at a glance.  The
       punctuation characters ':', ';' and ',' are also ignored.

   Poll versus Skip
       The 'poll' verb tells fetchmail to query this host when it is run with
       no arguments.  The 'skip' verb tells fetchmail not to poll this host
       unless it is explicitly named on the command line.  (The 'skip' verb
       allows you to experiment with test entries safely, or easily disable
       entries for hosts that are temporarily down.)


KEYWORD/OPTION SUMMARY
       Here are the legal options.  Keyword suffixes enclosed in square
       brackets are optional.  Those corresponding to short command-line
       options are followed by '-' and the appropriate option letter.  If
       option is only relevant to a single mode of operation, it is noted as
       's' or 'm' for singledrop- or multidrop-mode, respectively.

       Here are the legal global options:


       Keyword             Opt   Mode   Function
       --------------------------------------------------------------------
       set daemon          -d           Set a background poll interval in
                                        seconds.
       set postmaster                   Give the name of the last-resort
                                        mail recipient (default: user
                                        running fetchmail, "postmaster" if
                                        run by the root user)
       set    bouncemail                Direct error mail to the sender
                                        (default)
       set no bouncemail                Direct error mail to the local
                                        postmaster (as per the
                                        'postmaster' global option above).
       set no spambounce                Do not bounce spam-blocked mail
                                        (default).
       set    spambounce                Bounce blocked spam-blocked mail
                                        (as per the 'antispam' user
                                        option) back to the destination as
                                        indicated by the 'bouncemail'
                                        global option.  Warning: Do not
                                        use this to bounce spam back to
                                        the sender - most spam is sent
                                        with false sender address and thus
                                        this option hurts innocent
                                        bystanders.
       set no softbounce                Delete permanently undeliverable
                                        mail. It is recommended to use
                                        this option if the configuration
                                        has been thoroughly tested.
       set    softbounce                Keep permanently undeliverable
                                        mail as though a temporary error
                                        had occurred (default).
       set logfile         -L           Name of a file to append error and
                                        status messages to.  Only
                                        effective in daemon mode and if
                                        fetchmail detaches.  If effective,
                                        overrides set syslog.
       set pidfile         -p           Name of the PID file.
       set idfile          -i           Name of the file to store UID
                                        lists in.
       set    syslog                    Do error logging through
                                        syslog(3). May be overridden by
                                        set logfile.
       set no syslog                    Turn off error logging through
                                        syslog(3). (default)
       set properties                   String value that is ignored by
                                        fetchmail (may be used by
                                        extension scripts).

       Here are the legal server options:


       Keyword          Opt   Mode   Function
       -----------------------------------------------------------------
       via                           Specify DNS name of mail server,
                                     overriding poll name
       proto[col]       -p           Specify protocol (case
                                     insensitive): POP2, POP3, IMAP,
                                     APOP, KPOP
       local[domains]         m      Specify domain(s) to be regarded
                                     as local
       port                          Specify TCP/IP service port
                                     (obsolete, use 'service' instead).
       service          -P           Specify service name (a numeric
                                     value is also allowed and
                                     considered a TCP/IP port number).
       auth[enticate]                Set authentication type (default
                                     'any')


       timeout          -t           Server inactivity timeout in
                                     seconds (default 300)
       envelope         -E    m      Specify envelope-address header
                                     name
       no envelope            m      Disable looking for envelope
                                     address
       qvirtual         -Q    m      Qmail virtual domain prefix to
                                     remove from user name
       aka                    m      Specify alternate DNS names of
                                     mail server
       interface        -I           specify IP interface(s) that must
                                     be up for server poll to take
                                     place
       monitor          -M           Specify IP address to monitor for
                                     activity
       plugin                        Specify command through which to
                                     make server connections.
       plugout                       Specify command through which to
                                     make listener connections.
       dns                    m      Enable DNS lookup for multidrop
                                     (default)
       no dns                 m      Disable DNS lookup for multidrop
       checkalias             m      Do comparison by IP address for
                                     multidrop
       no checkalias          m      Do comparison by name for
                                     multidrop (default)
       uidl             -U           Force POP3 to use client-side
                                     UIDLs (recommended)
       no uidl                       Turn off POP3 use of client-side
                                     UIDLs (default)
       interval                      Only check this site every N poll
                                     cycles; N is a numeric argument.
       tracepolls                    Add poll tracing information to
                                     the Received header
       principal                     Set Kerberos principal (only
                                     useful with IMAP and kerberos)
       esmtpname                     Set name for RFC2554
                                     authentication to the ESMTP
                                     server.
       esmtppassword                 Set password for RFC2554
                                     authentication to the ESMTP
                                     server.
       bad-header                    How to treat messages with a bad
                                     header. Can be reject (default) or
                                     accept.

       Here are the legal user descriptions and options:


       Keyword            Opt   Mode               Function
       -------------------------------------------------------------------------------
       user[name]         -u                       This is the user description and
                                                   must come first after server
                                                   description and after possible
                                                   server options, and before user
                                                   options.

                                                   It sets the remote user name if by
                                                   itself or followed by 'there', or
                                                   the local user name if followed by
                                                   'here'.
       is                                          Connect local and remote user
                                                   names
       to                                          Connect local and remote user
                                                   names
       pass[word]                                  Specify remote account password
       ssl                                         Connect to server over the
                                                   specified base protocol using SSL
                                                   encryption

       sslcert                                     Specify file for client side
                                                   public SSL certificate
       sslcertck                                   Enable strict certificate checking
                                                   and abort connection on failure.
                                                   Default only since fetchmail
                                                   v6.4.0.
       no sslcertck                                Disable strict certificate
                                                   checking and permit connections to
                                                   continue on failed verification.
                                                   Discouraged. Should only be used
                                                   together with sslfingerprint.
       sslcertfile                                 Specify file with trusted CA
                                                   certificates
       sslcertpath                                 Specify c_rehash-ed directory with
                                                   trusted CA certificates.
       sslfingerprint           Specify the
                                expected server
                                certificate
                                finger print
                                from an MD5
                                hash. Fetchmail
                                will disconnect
                                and log an error
                                if it does not
                                match.
       sslkey                                      Specify file for client side
                                                   private SSL key
       sslproto                                    Force ssl protocol for connection
       folder             -r                       Specify remote folder to query
       smtphost           -S                       Specify smtp host(s) to forward to
       fetchdomains             m                  Specify domains for which mail
                                                   should be fetched
       smtpaddress        -D                       Specify the domain to be put in
                                                   RCPT TO lines
       smtpname                                    Specify the user and domain to be
                                                   put in RCPT TO lines
       antispam           -Z                       Specify what SMTP returns are
                                                   interpreted as spam-policy blocks
       mda                -m                       Specify MDA for local delivery
       bsmtp                                       Specify BSMTP batch file to append
                                                   to
       preconnect                                  Command to be executed before each
                                                   connection
       postconnect                                 Command to be executed after each
                                                   connection
       keep               -k                       Do not delete seen messages from
                                                   server (for POP3, uidl is
                                                   recommended)
       flush              -F                       Flush all seen messages before
                                                   querying (DANGEROUS)
       limitflush                                  Flush all oversized messages
                                                   before querying
       fetchall           -a                       Fetch all messages whether seen or
                                                   not
       rewrite                                     Rewrite destination addresses for
                                                   reply (default)
       stripcr                                     Strip carriage returns from ends
                                                   of lines
       forcecr                                     Force carriage returns at ends of
                                                   lines
       pass8bits                                   Force BODY=8BITMIME to ESMTP
                                                   listener
       dropstatus                                  Strip Status and X-Mozilla-Status
                                                   lines out of incoming mail
       dropdelivered                               Strip Delivered-To lines out of
                                                   incoming mail
       mimedecode                                  Convert quoted-printable to 8-bit
                                                   in MIME messages


       idle                                        Idle waiting for new messages
                                                   after each poll (IMAP only)
       no keep            -K                       Delete seen messages from server
                                                   (default)
       no flush                                    Do not flush all seen messages
                                                   before querying (default)
       no fetchall                                 Retrieve only new messages
                                                   (default)
       no rewrite                                  Do not rewrite headers
       no stripcr                                  Do not strip carriage returns
                                                   (default)
       no forcecr                                  Do not force carriage returns at
                                                   EOL (default)
       no pass8bits                                Do not force BODY=8BITMIME to
                                                   ESMTP listener (default)
       no dropstatus                               Do not drop Status headers
                                                   (default)
       no dropdelivered                            Do not drop Delivered-To headers
                                                   (default)
       no mimedecode                               Do not convert quoted-printable to
                                                   8-bit in MIME messages (default)
       no idle                                     Do not idle waiting for new
                                                   messages after each poll (IMAP
                                                   only)
       limit              -l                       Set message size limit
       warnings           -w                       Set message size warning interval
       batchlimit         -b                       Max # messages to forward in
                                                   single connect
       fetchlimit         -B                       Max # messages to fetch in single
                                                   connect
       fetchsizelimit                              Max # message sizes to fetch in
                                                   single transaction
       fastuidl                                    Use binary search for first unseen
                                                   message (POP3 only)
       expunge            -e                       Perform an expunge on every #th
                                                   message (IMAP and POP3 only)
       properties                                  String value is ignored by
                                                   fetchmail (may be used by
                                                   extension scripts)

       All user options must begin with a user description (user or username
       option) and follow all server descriptions and options.

       In the .fetchmailrc file, the 'envelope' string argument may be
       preceded by a whitespace-separated number.  This number, if specified,
       is the number of such headers to skip over (that is, an argument of 1
       selects the second header of the given type).  This is sometimes useful
       for ignoring bogus envelope headers created by an ISP's local delivery
       agent or internal forwards (through mail inspection systems, for
       instance).

   Keywords Not Corresponding To Option Switches
       The 'folder' and 'smtphost' options (unlike their command-line
       equivalents) can take a space- or comma-separated list of names
       following them.

       All options correspond to the obvious command-line arguments, except
       the following: 'via', 'interval', 'aka', 'is', 'to', 'dns'/'no dns',
       'checkalias'/'no checkalias', 'password', 'preconnect', 'postconnect',
       'localdomains', 'stripcr'/'no stripcr', 'forcecr'/'no forcecr',
       'pass8bits'/'no pass8bits' 'dropstatus/no dropstatus',
       'dropdelivered/no dropdelivered', 'mimedecode/no mimedecode', 'no
       idle', and 'no envelope'.

       The 'via' option is for if you want to have more than one configuration
       pointing at the same site.  If it is present, the string argument will
       be taken as the actual DNS name of the mail server host to query.  This
       will override the argument of poll, which can then simply be a distinct
       label for the configuration (e.g., what you would give on the command
       line to explicitly query this host).

       The 'interval' option (which takes a numeric argument) allows you to
       poll a server less frequently than the basic poll interval.  If you say
       'interval N' the server this option is attached to will only be queried
       every N poll intervals.

   Singledrop versus Multidrop options
       Please ensure you read the section titled THE USE AND ABUSE OF
       MULTIDROP MAILBOXES if you intend to use multidrop mode.

       The 'is' or 'to' keywords associate the following local (client)
       name(s) (or server-name to client-name mappings separated by =) with
       the mail server user name in the entry.  If an is/to list has '*' as
       its last name, unrecognized names are simply passed through. Note that
       until fetchmail version 6.3.4 inclusively, these lists could only
       contain local parts of user names (fetchmail would only look at the
       part before the @ sign). fetchmail versions 6.3.5 and newer support
       full addresses on the left hand side of these mappings, and they take
       precedence over any 'localdomains', 'aka', 'via' or similar mappings.

       A single local name can be used to support redirecting your mail when
       your username on the client machine is different from your name on the
       mail server.  When there is only a single local name, mail is forwarded
       to that local username regardless of the message's Received, To, Cc,
       and Bcc headers.  In this case, fetchmail never does DNS lookups.

       When there is more than one local name (or name mapping), fetchmail
       looks at the envelope header, if configured, and otherwise at the
       Received, To, Cc, and Bcc headers of retrieved mail (this is 'multidrop
       mode').  It looks for addresses with host name parts that match your
       poll name or your 'via', 'aka' or 'localdomains' options, and usually
       also for host name parts which DNS tells it are aliases of the mail
       server.  See the discussion of 'dns', 'checkalias', 'localdomains', and
       'aka' for details on how matching addresses are handled.

       If fetchmail cannot match any mail server usernames or localdomain
       addresses, the mail will be bounced.  Normally it will be bounced to
       the sender, but if the 'bouncemail' global option is off, the mail will
       go to the local postmaster instead.  (see the 'postmaster' global
       option). See also BUGS.

       The 'dns' option (normally on) controls the way addresses from
       multidrop mailboxes are checked.  On, it enables logic to check each
       host address that does not match an 'aka' or 'localdomains' declaration
       by looking it up with DNS.  When a mail server username is recognized
       attached to a matching host name part, its local mapping is added to
       the list of local recipients.

       The 'checkalias' option (normally off) extends the lookups performed by
       the 'dns' keyword in multidrop mode, providing a way to cope with
       remote MTAs that identify themselves using their canonical name, while
       they are polled using an alias.  When such a server is polled, checks
       to extract the envelope address fail, and fetchmail reverts to delivery
       using the To/Cc/Bcc headers (See below 'Header versus Envelope
       addresses').  Specifying this option instructs fetchmail to retrieve
       all the IP addresses associated with both the poll name and the name
       used by the remote MTA and to do a comparison of the IP addresses.
       This comes in handy in situations where the remote server undergoes
       frequent canonical name changes, that would otherwise require
       modifications to the rcfile.  'checkalias' has no effect if 'no dns' is
       specified in the rcfile.

       The 'aka' option is for use with multidrop mailboxes.  It allows you to
       pre-declare a list of DNS aliases for a server.  This is an
       optimization hack that allows you to trade space for speed.  When
       fetchmail, while processing a multidrop mailbox, grovels through
       message headers looking for names of the mail server, pre-declaring
       common ones can save it from having to do DNS lookups.  Note: the names
       you give as arguments to 'aka' are matched as suffixes -- if you
       specify (say) 'aka netaxs.com', this will match not just a host name
       netaxs.com, but any host name that ends with '.netaxs.com'; such as
       (say) pop3.netaxs.com and mail.netaxs.com.

       The 'localdomains' option allows you to declare a list of domains which
       fetchmail should consider local.  When fetchmail is parsing address
       lines in multidrop modes, and a trailing segment of a host name matches
       a declared local domain, that address is passed through to the listener
       or MDA unaltered (local-name mappings are not applied).

       If you are using 'localdomains', you may also need to specify 'no
       envelope', which disables fetchmail's normal attempt to deduce an
       envelope address from the Received line or X-Envelope-To header or
       whatever header has been previously set by 'envelope'.  If you set 'no
       envelope' in the defaults entry it is possible to undo that in
       individual entries by using 'envelope <string>'.  As a special case,
       'envelope "Received"' restores the default parsing of Received lines.

       The password option requires a string argument, which is the password
       to be used with the entry's server.

       The 'preconnect' keyword allows you to specify a shell command to be
       executed just before each time fetchmail establishes a mail server
       connection.  This may be useful if you are attempting to set up secure
       POP connections with the aid of ssh(1).  If the command returns a
       nonzero status, the poll of that mail server will be aborted.

       Similarly, the 'postconnect' keyword similarly allows you to specify a
       shell command to be executed just after each time a mail server
       connection is taken down.

       The 'forcecr' option controls whether lines terminated by LF only are
       given CRLF termination before forwarding.  Strictly speaking RFC821
       requires this, but few MTAs enforce the requirement so this option is
       normally off (only one such MTA, qmail, is in significant use at time
       of writing).

       The 'stripcr' option controls whether carriage returns are stripped out
       of retrieved mail before it is forwarded.  It is normally not necessary
       to set this, because it defaults to 'on' (CR stripping enabled) when
       there is an MDA declared but 'off' (CR stripping disabled) when
       forwarding is via SMTP.  If 'stripcr' and 'forcecr' are both on,
       'stripcr' will override.

       The 'pass8bits' option exists to cope with Microsoft mail programs that
       stupidly slap a "Content-Transfer-Encoding: 7bit" on everything.  With
       this option off (the default) and such a header present, fetchmail
       declares BODY=7BIT to an ESMTP-capable listener; this causes problems
       for messages actually using 8-bit ISO or KOI-8 character sets, which
       will be garbled by having the high bits of all characters stripped.  If
       'pass8bits' is on, fetchmail is forced to declare BODY=8BITMIME to any
       ESMTP-capable listener.  If the listener is 8-bit-clean (as all the
       major ones now are) the right thing will probably result.

       The 'dropstatus' option controls whether nonempty Status and X-Mozilla-
       Status lines are retained in fetched mail (the default) or discarded.
       Retaining them allows your MUA to see what messages (if any) were
       marked seen on the server.  On the other hand, it can confuse some new-
       mail notifiers, which assume that anything with a Status line in it has
       been seen.  (Note: the empty Status lines inserted by some buggy POP
       servers are unconditionally discarded.)

       The 'dropdelivered' option controls whether Delivered-To headers will
       be kept in fetched mail (the default) or discarded. These headers are
       added by qmail and Postfix mail servers in order to avoid mail loops
       but may get in your way if you try to "mirror" a mail server within the
       same domain. Use with caution.

       The 'mimedecode' option controls whether MIME messages using the
       quoted-printable encoding are automatically converted into pure 8-bit
       data. If you are delivering mail to an ESMTP-capable, 8-bit-clean
       listener (that includes all of the major MTAs like sendmail), then this
       will automatically convert quoted-printable message headers and data
       into 8-bit data, making it easier to understand when reading mail. If
       your e-mail programs know how to deal with MIME messages, then this
       option is not needed.  The mimedecode option is off by default, because
       doing RFC2047 conversion on headers throws away character-set
       information and can lead to bad results if the encoding of the headers
       differs from the body encoding.

       The 'idle' option is intended to be used with IMAP servers supporting
       the RFC2177 IDLE command extension, but does not strictly require it.
       If it is enabled, and fetchmail detects that IDLE is supported, an IDLE
       will be issued at the end of each poll.  This will tell the IMAP server
       to hold the connection open and notify the client when new mail is
       available.  If IDLE is not supported, fetchmail will simulate it by
       periodically issuing NOOP. If you need to poll a link frequently, IDLE
       can save bandwidth by eliminating TCP/IP connects and LOGIN/LOGOUT
       sequences. On the other hand, an IDLE connection will eat almost all of
       your fetchmail's time, because it will never drop the connection and
       allow other polls to occur unless the server times out the IDLE.  It
       also does not work with multiple folders; only the first folder will
       ever be polled.

       The 'properties' option is an extension mechanism.  It takes a string
       argument, which is ignored by fetchmail itself.  The string argument
       may be used to store configuration information for scripts which
       require it.  In particular, the output of '--configdump' option will
       make properties associated with a user entry readily available to a
       Python script.

   Miscellaneous Run Control Options
       The words 'here' and 'there' have useful English-like significance.
       Normally 'user eric is esr' would mean that mail for the remote user
       'eric' is to be delivered to 'esr', but you can make this clearer by
       saying 'user eric there is esr here', or reverse it by saying 'user esr
       here is eric there'

       Legal protocol identifiers for use with the 'protocol' keyword are:

           auto (or AUTO) (legacy, to be removed from future release)
           pop2 (or POP2) (legacy, to be removed from future release)
           pop3 (or POP3)
           sdps (or SDPS)
           imap (or IMAP)
           apop (or APOP)
           kpop (or KPOP)


       Legal authentication types are 'any', 'password', 'kerberos',
       'kerberos_v4', 'kerberos_v5' and 'gssapi', 'cram-md5', 'otp', 'msn'
       (only for POP3), 'ntlm', 'ssh', 'external' (only IMAP).  The 'password'
       type specifies authentication by normal transmission of a password (the
       password may be plain text or subject to protocol-specific encryption
       as in CRAM-MD5); 'kerberos' tells fetchmail to try to get a Kerberos
       ticket at the start of each query instead, and send an arbitrary string
       as the password; and 'gssapi' tells fetchmail to use GSSAPI
       authentication.  See the description of the 'auth' keyword for more.

       Specifying 'kpop' sets POP3 protocol over port 1109 with Kerberos V4
       authentication.  These defaults may be overridden by later options.

       There are some global option statements: 'set logfile' followed by a
       string sets the same global specified by --logfile.  A command-line
       --logfile option will override this. Note that --logfile is only
       effective if fetchmail detaches itself from the terminal and the
       logfile already exists before fetchmail is run, and it overrides
       --syslog in this case.  Also, 'set daemon' sets the poll interval as
       --daemon does.  This can be overridden by a command-line --daemon
       option; in particular --daemon 0 can be used to force foreground
       operation. The 'set postmaster' statement sets the address to which
       multidrop mail defaults if there are no local matches.  Finally, 'set
       syslog' sends log messages to syslogd(8).


DEBUGGING FETCHMAIL
   Fetchmail crashing
       There are various ways in that fetchmail may "crash", i. e. stop
       operation suddenly and unexpectedly. A "crash" usually refers to an
       error condition that the software did not handle by itself. A well-
       known failure mode is the "segmentation fault" or "signal 11" or
       "SIGSEGV" or just "segfault" for short. These can be caused by hardware
       or by software problems. Software-induced segfaults can usually be
       reproduced easily and in the same place, whereas hardware-induced
       segfaults can go away if the computer is rebooted, or powered off for a
       few hours, and can happen in random locations even if you use the
       software the same way.

       For solving hardware-induced segfaults, find the faulty component and
       repair or replace it.  The Sig11 FAQ <https://www.bitwizard.nl/sig11/>
       may help you with details.

       For solving software-induced segfaults, the developers may need a
       "stack backtrace".


   Enabling fetchmail core dumps
       By default, fetchmail suppresses core dumps as these might contain
       passwords and other sensitive information. For debugging fetchmail
       crashes, obtaining a "stack backtrace" from a core dump is often the
       quickest way to solve the problem, and when posting your problem on a
       mailing list, the developers may ask you for a "backtrace".

       1. To get useful backtraces, fetchmail needs to be installed without
       getting stripped of its compilation symbols.  Unfortunately, most
       binary packages that are installed are stripped, and core files from
       symbol-stripped programs are worthless. So you may need to recompile
       fetchmail. On many systems, you can type

               file `which fetchmail`

       to find out if fetchmail was symbol-stripped or not. If yours was
       unstripped, fine, proceed, if it was stripped, you need to recompile
       the source code first. You do not usually need to install fetchmail in
       order to debug it.

       2. The shell environment that starts fetchmail needs to enable core
       dumps. The key is the "maximum core (file) size" that can usually be
       configured with a tool named "limit" or "ulimit". See the documentation
       for your shell for details. In the popular bash shell, "ulimit -Sc
       unlimited" will allow the core dump.

       3. You need to tell fetchmail, too, to allow core dumps. To do this,
       run fetchmail with the -d0 -v options.  It is often easier to also add
       --nosyslog -N as well.

       Finally, you need to reproduce the crash. You can just start fetchmail
       from the directory where you compiled it by typing ./fetchmail, so the
       complete command line will start with ./fetchmail -Nvd0 --nosyslog and
       perhaps list your other options.

       After the crash, run your debugger to obtain the core dump.  The
       debugger will often be GNU GDB, you can then type (adjust paths as
       necessary) gdb ./fetchmail fetchmail.core and then, after GDB has
       started up and read all its files, type backtrace full, save the output
       (copy & paste will do, the backtrace will be read by a human) and then
       type quit to leave gdb.  Note: on some systems, the core files have
       different names, they might contain a number instead of the program
       name, or number and name, but it will usually have "core" as part of
       their name.


INTERACTION WITH RFC 822
       When trying to determine the originating address of a message,
       fetchmail looks through headers in the following order:

               Return-Path:
               Resent-Sender: (ignored if it does not contain an @ or !)
               Sender: (ignored if it does not contain an @ or !)
               Resent-From:
               From:
               Reply-To:
               Apparently-From:

       The originating address is used for logging, and to set the MAIL FROM
       address when forwarding to SMTP.  This order is intended to cope
       gracefully with receiving mailing list messages in multidrop mode. The
       intent is that if a local address does not exist, the bounce message
       will not be returned blindly to the author or to the list itself, but
       rather to the list manager (which is less annoying).

       In multidrop mode, destination headers are processed as follows: First,
       fetchmail looks for the header specified by the 'envelope' option in
       order to determine the local recipient address. If the mail is
       addressed to more than one recipient, the Received line will not
       contain any information regarding recipient addresses.

       Then fetchmail looks for the Resent-To:, Resent-Cc:, and Resent-Bcc:
       lines.  If they exist, they should contain the final recipients and
       have precedence over their To:/Cc:/Bcc: counterparts.  If the Resent-*
       lines do not exist, the To:, Cc:, Bcc: and Apparently-To: lines are
       looked for. (The presence of a Resent-To: is taken to imply that the
       person referred by the To: address has already received the original
       copy of the mail.)


CONFIGURATION EXAMPLES
       Note that although there are password declarations in a good many of
       the examples below, this is mainly for illustrative purposes.  We
       recommend stashing account/password pairs in your $HOME/.netrc file,
       where they can be used not just by fetchmail but by ftp(1) and other
       programs.

       The basic format is:


              poll SERVERNAME protocol PROTOCOL username NAME password
              PASSWORD


       Example:


              poll pop.provider.net protocol pop3 username "jsmith" password "secret1"


       Or, using some abbreviations:


              poll pop.provider.net proto pop3 user "jsmith" password "secret1"


       Multiple servers may be listed:


              poll pop.provider.net proto pop3 user "jsmith" pass "secret1"
              poll other.provider.net proto pop2 user "John.Smith" pass "My^Hat"


       Here is the same version with more whitespace and some noise words:


              poll pop.provider.net proto pop3
                   user "jsmith", with password secret1, is "jsmith" here;
              poll other.provider.net proto pop2:
                   user "John.Smith", with password "My^Hat", is "John.Smith" here;


       If you need to include whitespace in a parameter string or start the
       latter with a number, enclose the string in double quotes.  Thus:


              poll mail.provider.net with proto pop3:
                   user "jsmith" there has password "4u but u cannot krak this"
                   is jws here and wants mda "/bin/mail"


       You may have an initial server description headed by the keyword
       'defaults' instead of 'poll' followed by a name.  Such a record is
       interpreted as defaults for all queries to use. It may be overwritten
       by individual server descriptions.  So, you could write:


              defaults proto pop3
                   user "jsmith"
              poll pop.provider.net
                   pass "secret1"
              poll mail.provider.net
                   user "jjsmith" there has password "secret2"


       It is possible to specify more than one user per server.  The 'user'
       keyword leads off a user description, and every user specification in a
       multi-user entry must include it.  Here is an example:


              poll pop.provider.net proto pop3 port 3111
                   user "jsmith" with pass "secret1" is "smith" here
                   user jones with pass "secret2" is "jjones" here keep


       This associates the local username 'smith' with the pop.provider.net
       username 'jsmith' and the local username 'jjones' with the
       pop.provider.net username 'jones'.  Mail for 'jones' is kept on the
       server after download.


       Here is what a simple retrieval configuration for a multidrop mailbox
       looks like:


              poll pop.provider.net:
                   user maildrop with pass secret1 to golux 'hurkle'='happy' snark here


       This says that the mailbox of account 'maildrop' on the server is a
       multidrop box, and that messages in it should be parsed for the server
       user names 'golux', 'hurkle', and 'snark'.  It further specifies that
       'golux' and 'snark' have the same name on the client as on the server,
       but mail for server user 'hurkle' should be delivered to client user
       'happy'.


       Note that fetchmail, until version 6.3.4, did NOT allow full
       user@domain specifications here, these would never match.  Fetchmail
       6.3.5 and newer support user@domain specifications on the left-hand
       side of a user mapping.


       Here is an example of another kind of multidrop connection:


              poll pop.provider.net localdomains loonytoons.org toons.org
                   envelope X-Envelope-To
                   user maildrop with pass secret1 to * here


       This also says that the mailbox of account 'maildrop' on the server is
       a multidrop box.  It tells fetchmail that any address in the
       loonytoons.org or toons.org domains (including sub-domain addresses
       like 'joe@daffy.loonytoons.org') should be passed through to the local
       SMTP listener without modification.  Be careful of mail loops if you do
       this!


       Here is an example configuration using ssh and the plugin option.  The
       queries are made directly on the stdin and stdout of imapd via ssh.
       Note that in this setup, IMAP authentication can be skipped.


              poll mailhost.net with proto imap:
                   plugin "ssh %h /usr/sbin/imapd" auth ssh;
                   user esr is esr here


THE USE AND ABUSE OF MULTIDROP MAILBOXES
       Use the multiple-local-recipients feature with caution -- it can bite.
       All multidrop features are ineffective in ETRN and ODMR modes.

       Also, note that in multidrop mode duplicate mails may be suppressed.  A
       piece of mail is considered duplicate if it does not have a discernible
       envelope recipient address, has the same header as the message
       immediately preceding and more than one addressee.  Such runs of
       messages may be generated when copies of a message addressed to
       multiple users are delivered to a multidrop box. (To be precise,
       fetchmail 6.2.5 through 6.4.X use an MD5 hash of the raw message
       header, and only fetchmail 6.4.16+ document this properly.  Fetchmail
       5.0.8 (1999-09-14) through 6.2.4 used only the Message-ID header.
       5.0.7 and older did not suppress duplicates.)

       Note that this duplication killer code checking the entire header is
       very restrictive and may not suppress many duplicates in practice - for
       instance, if some X-Original-To or Delivered-To header differs.  This
       is intentional and correct in such situations: wherever envelope
       information is available, it should be used for reliable delivery of
       mailing list and blind carbon copy (Bcc) messages. See the subsection
       Duplicate suppression below for suggestions.


   Header versus Envelope addresses
       The fundamental problem is that by having your mail server toss several
       peoples' mail in a single maildrop box, you may have thrown away
       potentially vital information about who each piece of mail was actually
       addressed to (the 'envelope address', as opposed to the header
       addresses in the RFC822 To/Cc headers - the Bcc is not available at the
       receiving end).  This 'envelope address' is the address you need in
       order to reroute mail properly.

       Sometimes fetchmail can deduce the envelope address.  If the mail
       server MTA is sendmail and the item of mail had just one recipient, the
       MTA will have written a 'by/for' clause that gives the envelope
       addressee into its Received header. But this does not work reliably for
       other MTAs, nor if there is more than one recipient.  By default,
       fetchmail looks for envelope addresses in these lines; you can restore
       this default with -E "Received" or 'envelope Received'.

       As a better alternative, some SMTP listeners and/or mail servers insert
       a header in each message containing a copy of the envelope addresses.
       This header (when it exists) is often 'X-Original-To', 'Delivered-To'
       or 'X-Envelope-To'.  Fetchmail's assumption about this can be changed
       with the -E or 'envelope' option.  Note that writing an envelope header
       of this kind exposes the names of recipients (including blind-copy
       recipients) to all receivers of the messages, so the upstream must
       store one copy of the message per recipient to avoid becoming a privacy
       problem.

       Postfix, since version 2.0, writes an X-Original-To: header which
       contains a copy of the envelope as it was received.

       Qmail and Postfix generally write a 'Delivered-To' header upon
       delivering the message to the mail spool and use it to avoid mail
       loops.  Qmail virtual domains however will prefix the user name with a
       string that normally matches the user's domain. To remove this prefix
       you can use the -Q or 'qvirtual' option.

       Sometimes, unfortunately, neither of these methods works.  That is the
       point when you should contact your ISP and ask them to provide such an
       envelope header, and you should not use multidrop in this situation.
       When they all fail, fetchmail must fall back on the contents of To/Cc
       headers (Bcc headers are not available - see below) to try to determine
       recipient addressees -- and these are unreliable.  In particular,
       mailing-list software often ships mail with only the list broadcast
       address in the To: header.

       Note that a future version of fetchmail may remove To/Cc parsing!

       When fetchmail cannot deduce a recipient address that is local, and the
       intended recipient address was anyone other than fetchmail's invoking
       user, mail will get lost.  This is what makes the multidrop feature
       risky without proper envelope information.

       A related problem is that when you blind-copy a mail message, the Bcc
       information is carried only as envelope address (it is removed from the
       headers by the sending mail server, so fetchmail can see it only if
       there is an X-Envelope-To header).  Thus, blind-copying to someone who
       gets mail over a fetchmail multidrop link will fail unless the mail
       server host routinely writes X-Envelope-To or an equivalent header into
       messages in your maildrop.

       In conclusion, mailing lists and Bcc'd mail can only work if the server
       you are fetching from

       (1)    stores one copy of the message per recipient in your domain and

       (2)    records the envelope information in a special header
              (X-Original-To, Delivered-To, X-Envelope-To).


   Good Ways To Use Multidrop Mailboxes
       Multiple local names can be used to administer a mailing list from the
       client side of a fetchmail collection.  Suppose your name is 'esr', and
       you want to both pick up your own mail and maintain a mailing list
       called (say) "fetchmail-friends", and you want to keep the alias list
       on your client machine.

       On your server, you can alias 'fetchmail-friends' to 'esr'; then, in
       your .fetchmailrc, declare 'to esr fetchmail-friends here'.  Then, when
       mail including 'fetchmail-friends' as a local address gets fetched, the
       list name will be appended to the list of recipients your SMTP listener
       sees.  Therefore it will undergo alias expansion locally.  Be sure to
       include 'esr' in the local alias expansion of fetchmail-friends, or you
       will never see mail sent only to the list.  Also be sure that your
       listener has the "me-too" option set (sendmail's -oXm command-line
       option or OXm declaration) so your name is not removed from alias
       expansions in messages you send.

       This trick is not without its problems, however.  You will begin to see
       this when a message comes in that is addressed only to a mailing list
       you do not have declared as a local name.  Each such message will
       feature an 'X-Fetchmail-Warning' header which is generated because
       fetchmail cannot find a valid local name in the recipient addresses.
       Such messages default (as was described above) to being sent to the
       local user running fetchmail, but the program has no way to know that
       this is actually the right thing.


   Bad Ways To Abuse Multidrop Mailboxes
       Multidrop mailboxes and fetchmail serving multiple users in daemon mode
       do not mix.  The problem, again, is mail from mailing lists, which
       typically does not have an individual recipient address on it.   Unless
       fetchmail can deduce an envelope address, such mail will only go to the
       account running fetchmail (probably root).  Also, blind-copied users
       are very likely never to see their mail at all.

       If you are tempted to use fetchmail to retrieve mail for multiple users
       from a single mail drop via POP or IMAP, think again (and reread the
       section on header and envelope addresses above).  It would be smarter
       to just let the mail sit in the mail server's queue and use fetchmail's
       ETRN or ODMR modes to trigger SMTP sends periodically (of course, this
       means you have to poll more frequently than the mail server's expiry
       period).  If you cannot arrange this, try setting up a UUCP feed.

       If you absolutely must use multidrop for this purpose, make sure your
       mail server writes an envelope-address header that fetchmail can see.
       Otherwise you will lose mail and it will come back to haunt you.


   Speeding Up Multidrop Checking
       Normally, when multiple users are declared fetchmail extracts recipient
       addresses as described above and checks each host part with DNS to see
       if it is an alias of the mail server.  If so, the name mappings
       described in the "to ... here" declaration are done and the mail
       locally delivered.

       This is a convenient but also slow method.  To speed it up, pre-declare
       mail server aliases with 'aka'; these are checked before DNS lookups
       are done.  If you are certain your aka list contains all DNS aliases of
       the mail server (and all MX names pointing at it - note this may change
       in a future version) you can declare 'no dns' to suppress DNS lookups
       entirely and only match against the aka list.


   Duplicate suppression on multidrop
       If fetchmail's duplicate suppression code does not kick in for your
       multidrop mail account, other options is using sieve, or for instance
       Courier's maildrop package (and in particular, its reformail program
       with the -D option) as the delivery agent (either from fetchmail, or
       from your local mail server that fetchmail injects into).


SOCKS
       Support for socks4/5 is a compile time configuration option. Once
       compiled in, fetchmail will always use the socks libraries and
       configuration on your system, there are no run-time switches in
       fetchmail - but you can still configure SOCKS: you can specify which
       SOCKS configuration file is used in the SOCKS_CONF environment
       variable.

       For instance, if you wanted to bypass the SOCKS proxy altogether and
       have fetchmail connect directly, you could just pass
       SOCKS_CONF=/dev/null in the environment, for example (add your usual
       command line options - if any - to the end of this line):

       env SOCKS_CONF=/dev/null fetchmail


EXIT CODES
       To facilitate the use of fetchmail in shell scripts, an exit status
       code is returned to give an indication of what occurred during a given
       connection.

       The exit codes returned by fetchmail are as follows:

       0      One or more messages were successfully retrieved (or, if the -c
              option was selected, were found waiting but not retrieved).

       1      There was no mail awaiting retrieval.  (There may have been old
              mail still on the server but not selected for retrieval.) If you
              do not want "no mail" to be an error condition (for instance,
              for cron jobs), use a POSIX-compliant shell and add

              || [ $? -eq 1 ]

              to the end of the fetchmail command line, note that this leaves
              0 untouched, maps 1 to 0, and maps all other codes to 1. See
              also item #C8 in the FAQ.

       2      An error was encountered when attempting to open a socket to
              retrieve mail.  If you do not know what a socket is, do not
              worry about it -- just treat this as an 'unrecoverable error'.
              This error can also be because a protocol fetchmail wants to use
              is not listed in /etc/services.

       3      The user authentication step failed.  This usually means that a
              bad user-id, password, or APOP id was specified.  Or it may mean
              that you tried to run fetchmail under circumstances where it did
              not have standard input attached to a terminal and could not
              prompt for a missing password.

       4      Some sort of fatal protocol error was detected.

       5      There was a syntax error in the arguments to fetchmail, or a
              pre- or post-connect command failed.

       6      The run control file had bad permissions.

       7      There was an error condition reported by the server.  Can also
              fire if fetchmail timed out while waiting for the server.

       8      Client-side exclusion error.  This means fetchmail either found
              another copy of itself already running, or failed in such a way
              that it is not sure whether another copy is running.

       9      The user authentication step failed because the server responded
              "lock busy".  Try again after a brief pause!  This error is not
              implemented for all protocols, nor for all servers.  If not
              implemented for your server, "3" will be returned instead, see
              above.  May be returned when talking to qpopper or other servers
              that can respond with "lock busy" or some similar text
              containing the word "lock".

       10     The fetchmail run failed while trying to do an SMTP port open or
              transaction.

       11     Fatal DNS error.  Fetchmail encountered an error while
              performing a DNS lookup at startup and could not proceed.

       12     BSMTP batch file could not be opened.

       13     Poll terminated by a fetch limit (see the --fetchlimit option).

       14     Server busy indication.

       23     Internal error.  You should see a message on standard error with
              details.

       24 - 26, 28, 29
              These are internal codes and should not appear externally.

       When fetchmail queries more than one host, return status is 0 if any
       query successfully retrieved mail. Otherwise the returned error status
       is that of the last host queried.


FILES
       ~/.fetchmailrc, $HOME/.fetchmailrc, $HOME_ETC/.fetchmailrc,
       $FETCHMAILHOME/fetchmailrc
            default run control file (location can be overridden with
            environment variables)

       ~/.fetchids, $HOME/.fetchids, $HOME_ETC/.fetchids,
       $FETCHMAILHOME/.fetchids
            default location of file recording last message UIDs seen per
            host.  (location can be overridden with environment variables)

       ~/.fetchmail.pid, $HOME/.fetchmail.pid, $HOME_ETC/.fetchmail.pid,
       $FETCHMAILHOME/fetchmail.pid
            default location of lock file (sometimes called pidfile or PID
            file, see option pidfile) to help prevent concurrent runs (non-
            root mode).  (location can be overridden with environment
            variables)

       ~/.netrc, $HOME/.netrc, $HOME_ETC/.netrc
            your FTP run control file, which (if present) will be searched for
            passwords as a last resort before prompting for one interactively.
            (location can be overridden with environment variables)

       /var/run/fetchmail.pid
            lock file (pidfile) to help prevent concurrent runs (root mode,
            Linux systems).

       /etc/fetchmail.pid
            lock file (pidfile) to help prevent concurrent runs (root mode,
            systems without /var/run).


ENVIRONMENT
       Fetchmail's behavior can be altered by providing it with environment
       variables.  Some may alter the operation of libraries that fetchmail
       links against, for instance, OpenSSL.  Note that in daemon mode, you
       will need to quit the background daemon process and start a new
       fetchmail daemon for environment changes to take effect.

       FETCHMAILHOME
              If this environment variable is set to a valid and existing
              directory name, fetchmail will read $FETCHMAILHOME/fetchmailrc
              (the dot is missing in this case), $FETCHMAILHOME/.fetchids
              (keeping its dot) and $FETCHMAILHOME/fetchmail.pid (without dot)
              rather than from the user's home directory.  The .netrc file is
              always looked for in the invoking user's home directory (or
              $HOME_ETC) regardless of FETCHMAILHOME's setting.


       FETCHMAILUSER
              If this environment variable is set, it is used as the name of
              the calling user (default local name) for purposes such as
              mailing error notifications.  Otherwise, if either the LOGNAME
              or USER variable is correctly set (e.g., the corresponding UID
              matches the session user ID) then that name is used as the
              default local name.  Otherwise getpwuid(3) must be able to
              retrieve a password entry for the session ID (this elaborate
              logic is designed to handle the case of multiple names per user
              ID gracefully).


       FETCHMAIL_DISABLE_CBC_IV_COUNTERMEASURE
              (since v6.3.22): If this environment variable is set and not
              empty, fetchmail will disable a countermeasure against an SSL
              CBC IV attack (by setting SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS).
              This is a security risk, but may be necessary for connecting to
              certain non-standards-conforming servers.  See fetchmail's NEWS
              file and fetchmail-SA-2012-01.txt for details.  Earlier
              fetchmail versions (v6.3.21 and older) used to disable this
              countermeasure, but v6.3.22 no longer does that as a safety
              precaution.


       FETCHMAIL_POP3_FORCE_RETR
              (since v6.3.9): If this environment variable is defined at all
              (even if empty), fetchmail will forgo the POP3 TOP command and
              always use RETR. This can be used as a workaround when TOP does
              not work properly.


       FETCHMAIL_INCLUDE_DEFAULT_X509_CA_CERTS
              (since v6.3.17): If this environment variable is set and not
              empty, fetchmail will always load the default X.509 trusted
              certificate locations for SSL/TLS CA certificates, even if
              --sslcertfile and --sslcertpath are given.  The latter locations
              take precedence over the system default locations.  This is
              useful in case there are broken certificates in the system
              directories and the user has no administrator privileges to
              remedy the problem.


       FETCHMAIL_WOLFSSL_DEBUG
              (since v6.4.25): If fetchmail is compiled and linked with
              wolfSSL, if wolfSSL was built with --enable-debug, and if this
              environment variable is set and not empty, then enable wolfSSL's
              debug mode. This will emit huge amounts of debug output to
              stderr.


       HOME   (documented since 6.4.1): This variable is normally set to the
              user's home directory. If it is set to a different directory
              than what is in the password database, HOME takes precedence.


       HOME_ETC
              (documentation corrected to match behaviour of code since
              6.4.1): If the HOME_ETC variable is set, it will override
              fetchmail's idea of $HOME, i. e. fetchmail will read
              .fetchmailrc, .fetchids, .fetchmail.pid and .netrc from
              $HOME_ETC instead of $HOME (or if HOME is also unset, from the
              passwd file's home directory location).

              If HOME_ETC and FETCHMAILHOME are both set, FETCHMAILHOME takes
              precedence and HOME_ETC will be ignored.


       SOCKS_CONF
              (only if SOCKS support is compiled in) this variable is used by
              the socks library to find out which configuration file it should
              read. Set this to /dev/null to bypass the SOCKS proxy.


       SSL_CERT_DIR
              (with truly OpenSSL 1.1.1 compatible library): overrides
              OpenSSL's idea of the default trust directory or path (which
              contains individual certificate files and hashed symlinks), see
              the SSL_CTX_set_default_verify_paths(3) manual page for details,
              it may be in the openssl development package.  If using another
              library's OpenSSL compatibility interface, this may not work.
              Since this variable only specifies a default value, the option
              --sslcertpath takes precedence if given.


       SSL_CERT_FILE
              (with truly OpenSSL 1.1.1 compatible library): overrides
              OpenSSL's idea of the default trust certificate bundle file
              (which contains a concatenation of base64-encoded certificates
              in PEM format), see the SSL_CTX_set_default_verify_paths(3)
              manual page for details, it may be in the openssl development
              package.  If using another library's OpenSSL compatibility
              interface, this may not work.  Since this variable only
              specifies a default value, the option --sslcertfile takes
              precedence if given.


SIGNALS
       If a fetchmail daemon is running as root, SIGUSR1 wakes it up from its
       sleep phase and forces a poll of all non-skipped servers. For
       compatibility reasons, SIGHUP can also be used in 6.3.X but may not be
       available in future fetchmail versions.

       If fetchmail is running in daemon mode as non-root, use SIGUSR1 to wake
       it (this is so SIGHUP due to logout can retain the default action of
       killing it).

       Running fetchmail in foreground while a background fetchmail is running
       will do whichever of these is appropriate to wake it up.


BUGS, LIMITATIONS, AND KNOWN PROBLEMS
       Please check the NEWS file that shipped with fetchmail for more known
       bugs than those listed here.

       Fetchmail cannot handle user names that contain blanks after a "@"
       character, for instance "demonstr@ti on". These are rather uncommon and
       only hurt when using UID-based --keep setups, so the 6.X.Y versions of
       fetchmail will not be fixed.

       Fetchmail cannot handle configurations where you have multiple accounts
       that use the same server name and the same login. Any user@server
       combination must be unique.

       The assumptions that the DNS and in particular the checkalias options
       make are not often sustainable. For instance, it has become uncommon
       for an MX server to be a POP3 or IMAP server at the same time.
       Therefore the MX lookups may go away in a future release.

       The mda and plugin options interact badly.  In order to collect error
       status from the MDA, fetchmail has to change its normal signal handling
       so that dead plugin processes do not get reaped until the end of the
       poll cycle.  This can cause resource starvation if too many zombies
       accumulate.  So either do not deliver to a MDA using plugins or risk
       being overrun by an army of undead.

       The --interface option does not support IPv6 and it is doubtful if it
       ever will, since there is no portable way to query interface IPv6
       addresses.

       The RFC822 address parser used in multidrop mode chokes on some
       @-addresses that are technically legal but bizarre.  Strange uses of
       quoting and embedded comments are likely to confuse it.

       In a message with multiple envelope headers, only the last one
       processed will be visible to fetchmail.

       Use of some of these protocols requires that the program send
       unencrypted passwords over the TCP/IP connection to the mail server.
       This creates a risk that name/password pairs might be snaffled with a
       packet sniffer or more sophisticated monitoring software.  Under Linux
       and FreeBSD, the --interface option can be used to restrict polling to
       availability of a specific interface device with a specific local or
       remote IP address, but snooping is still possible if (a) either host
       has a network device that can be opened in promiscuous mode, or (b) the
       intervening network link can be tapped.  We recommend the use of ssh(1)
       tunnelling to not only shroud your passwords but encrypt the entire
       conversation.

       Use of the %F or %T escapes in an mda option could open a security
       hole, because they pass text manipulable by an attacker to a shell
       command.  Potential shell characters are replaced by '_' before
       execution.  The hole is further reduced by the fact that fetchmail
       temporarily discards any set-uid privileges it may have while running
       the MDA.  For maximum safety, however, do not use an mda command
       containing %F or %T when fetchmail is run from the root account itself.

       Fetchmail's method of sending bounces due to errors or spam-blocking
       and spam bounces requires that port 25 of localhost be available for
       sending mail via SMTP.

       If you modify ~/.fetchmailrc while a background instance is running and
       break the syntax, the background instance will die silently.
       Unfortunately, it cannot die noisily because we do not yet know whether
       syslog should be enabled.  On some systems, fetchmail dies quietly even
       if there is no syntax error; this seems to have something to do with
       buggy terminal ioctl code in the kernel.

       The -f - option (reading a configuration from stdin) is incompatible
       with the plugin option.

       The 'principal' option only handles Kerberos IV, not V.

       Interactively entered passwords are truncated after 63 characters. If
       you really need to use a longer password, you will have to use a
       configuration file.

       A backslash as the last character of a configuration file will be
       flagged as a syntax error rather than ignored.

       The BSMTP error handling is virtually nonexistent and may leave broken
       messages behind.

       Send comments, bug reports, gripes, and the like to the fetchmail-devel
       list <mailto:fetchmail-devel@lists.sourceforge.net>


       An fetchmail FAQ (in HTML form)
       <https://fetchmail.sourceforge.io/fetchmail-FAQ.html> is available at
       the fetchmail home page, it should also accompany your installation.


AUTHOR
       Fetchmail is currently maintained by Matthias Andree and Rob Funk with
       major assistance from Sunil Shetye (for code) and Rob MacGregor (for
       the mailing lists).

       Most of the code is from Eric S. Raymond
       <mailto:esr@snark.thyrsus.com>.  Too many other people to name here
       have contributed code and patches.

       This program is descended from and replaces popclient, by Carl Harris
       <mailto:ceharris@mal.com>; the internals have become quite different,
       but some of its interface design is directly traceable to that
       ancestral program.

       This manual page has been improved by Matthias Andree, R. Hannes
       Beinert, and Hector Garcia.


SEE ALSO
       README, README.SSL, README.SSL-SERVER, The Fetchmail FAQ
       <https://www.fetchmail.info/fetchmail-FAQ.html>, mutt(1), elm(1),
       mail(1), sendmail(8), popd(8), imapd(8), netrc(5), the fetchmail home
       page <https://www.fetchmail.info/>, (alternative URI)
       <https://fetchmail.sourceforge.io/>; the maildrop home page.
       <https://www.courier-mta.org/maildrop/>

APPLICABLE STANDARDS
       Note that this list is just a collection of references and not a
       statement as to the actual protocol conformance or requirements in
       fetchmail.

       SMTP/ESMTP:
            RFC 821, RFC 2821, RFC 1869, RFC 1652, RFC 1870, RFC 1983, RFC
            1985, RFC 2554.

       mail:
            RFC 822, RFC 2822, RFC 1123, RFC 1892, RFC 1894.

       POP2:
            RFC 937

       POP3:
            RFC 1081, RFC 1225, RFC 1460, RFC 1725, RFC 1734, RFC 1939, RFC
            1957, RFC 2195, RFC 2449.

       APOP:
            RFC 1939.

       RPOP:
            RFC 1081, RFC 1225.

       IMAP2/IMAP2BIS:
            RFC 1176, RFC 1732.

       IMAP4/IMAP4rev1:
            RFC 1730, RFC 1731, RFC 1732, RFC 2060, RFC 2061, RFC 2195, RFC
            2177, RFC 2683.

       ETRN:
            RFC 1985.

       ODMR/ATRN:
            RFC 2645.

       OTP: RFC 1938.

       LMTP:
            RFC 2033.

       GSSAPI:
            RFC 1508, RFC 1734, Generic Security Service Application Program
            Interface (GSSAPI)/Kerberos/Simple Authentication and Security
            Layer (SASL) Service Names
            <https://www.iana.org/assignments/gssapi-service-names/>.

       TLS: RFC 2595.



fetchmail 6.4.37                  2022-07-16                      FETCHMAIL(1)
