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 RFC 822)

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

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