ABOUT SETTING UP MAIL ON PPP-CONNECTED DIALUP MACHINES.
=======================================================

# This howto is distributed in the hope that it will be useful,        #
# but WITHOUT ANY WARRANTY; without even the implied warranty of       #
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.                 #

This howto is for you if you have a Linux machine that does not have a
permanent internet connection but rather uses dialup PPP to connect to
your internet service provider. A common problem is how to masquerade as
your ISP's mailhost to get

From: me@myispprovider.com

instead of

From: me@mylocalPPPmachine.nowhere

Another problem is how to send and receive mail.

1.) Setting up sendmail for masquerading
========================================

If you don't use sendmail, you're on your own. If you're using sendmail,
all you need to do is to replace your /etc/sendmail.cf with a new
sendmail.cf that you generate using the m4 files that come with any
(newer) sendmail source distribution.

In that distribution you'll find directories ./cf/cf, ./cf/domain,
../cf/feature, ... You first have to create an m4 config file for your
host. The file ./cf/README explains how to do that. If you don't want to
read it, here is a quick start with an m4 config file (myhost.mc) that
should be appropriate in most cases (if you don't use procmail, delete
the lines regarding procmail; BTW, redhat 4.2 uses procmail):

# myhost.mc
VERSIONID(`Put here some free text describing the version of this config file')
OSTYPE(linux)
DOMAIN(generic)
define(`SMART_HOST', `myispmailhost.com')dnl
FEATURE(masquerade_envelope)
MASQUERADE_AS(myispdomain)
define(`PROCMAIL_MAILER_PATH',`/usr/bin/procmail')dnl
define(`confCOPY_ERRORS_TO',`mylocalloginname')dnl
FEATURE(nouucp)
FEATURE(local_procmail)
MAILER(local)
MAILER(smtp)
MAILER(procmail)

In many cases, myispmailhost.com and myispdomain are the same:

Myispmailhost is the host that accepts SMTP connections on tcp port 25
and acts as a mail relay to the outer world (smart host). Very often
the name of a PPP connected machine does not have a valid entry in
DNS (domain name service), i.e. other machines that try to determine
your IP address using your hostname will get an error. Some domains
(notably AOL) won't accept mail from your host if they get such an
error. Therefore, you need to use a mail relay since otherwise you won't
be able to send mail to such domains. If you did not get the address of
a mail relay from your ISP provider, the best bet is to use the same
host that you were told to use as your POP server.

Myispdomain is what you want to see in your "From:" lines. For example,
if you choose

MASQUERADE_AS(isp.nowhere.com)

your "From:" lines will appear as

From: loginname@isp.nowhere.com

although the name of your PPP connected Unix machine is completely different.

After editing myhost.mc, put the file into ./cf/cf. Then cd to ./cf, call

m4 m4/cf.m4 cf/myhost.mc > sendmail.cf
su
cp sendmail.cf /etc
touch /etc/sendmail.cw

and restart sendmail. That's all.


2.) Setting up fetchmail
========================

Fetchmail is very good at downloading mail from your mailbox at your ISP
using POP3 (post office protocol version 3).

First get and install fetchmail (for example, from any sunsite
mirror). Configuring fetchmail means basically editing a file
~/.fetchmailrc. Here is my ~/.fetchmailrc:

-------------------------------------------------------------------
poll sirius.physik.TU-Berlin.DE protocol pop3:
	user henrik there has password ********, is henrik here;
-------------------------------------------------------------------

Replace "sirius..." with the name of your POP server (your ISP should
have told you which server to use). Of course, you have to change the
login names and the password.

Don't forget to set the file permissions to 600 using "chmod 600
~/.fetchmailrc" (otherwise other users can read your password).


3.) Automatically sending the sendmail queue and fetching mail at dialup
========================================================================

If you're sending mail while not being connected to the internet,
sendmail will append this mail to the mail queue. To automatically send
all mail in the queue whenever you connect to the net using PPP, add
this line to your /etc/ppp/ip-up:

  PATH=$PATH:/usr/sbin:/sbin
  export PATH
  sendmail -q

You probably want to fetch all your new mail whenever you connect,
so add this to /etc/ppp/ip-up (will fetch your mail on startup and
afterwards in intervals of 300 seconds):

  su -c 'fetchmail --daemon 300 --syslog;' henrik

(replace "henrik" with your local login name)

and add this to /etc/ppp/ip-down to automatically kill the fetchmail
daemon when you disconnect:

  PATH=$PATH:/usr/sbin:/sbin
  export PATH
  su -c "fetchmail --quit" henrik

That's all.

---------------------------------------------------------------------
Henrik Seidel, http://satchmo.physik.tu-berlin.de/~henrik/
TU Berlin, Inst. f. Theor. Physik, Sekr. PN 7-1, Hardenbergstr. 36
10623 Berlin, GERMANY, tel: +49-30-314-23000 fax: +49-30-314-21130
use "finger henrik@satchmo.physik.tu-berlin.de" to get my public pgp key
---------------------------------------------------------------------

