1) Check what happens if SMTP server doesn't like our HELO query

2) Do not allow mail server's on private networks like 192.168.*.*

3) OO interface

4) More correct syntax checking (better comformance to RFCs) (?)

5) Allow to users on 'perl Makefile.PM' specify test mailboxes that will be
tested on 'make test' (?) 

6) Allow specify DNS servers with which dns checks should be done.
