this in the mail.log file after trying to connect to the mail server via squirrelmail.
if it helps. i can send mail through the command line using:
mail rcordeiro@mars.av.it.pt
although i noticed it was going to mbox and not Maildir.
Problem?

Nov 15 14:52:02 mars imapd-ssl: Connection, ip=[::ffff:127.0.0.1]
Nov 15 14:52:02 mars imapd-ssl: LOGIN, user=rcordeiro, ip=[::ffff:127.0.0.1], protocol=IMAP
Nov 15 14:52:02 mars imapd-ssl: LOGOUT, user=rcordeiro, ip=[::ffff:127.0.0.1], headers=0, body=0, time=0, starttls=1
Nov 15 14:52:02 mars imapd-ssl: Connection, ip=[::ffff:127.0.0.1]
Nov 15 14:52:03 mars imapd-ssl: LOGIN, user=rcordeiro, ip=[::ffff:127.0.0.1], protocol=IMAP
Nov 15 14:52:03 mars imapd-ssl: Connection, ip=[::ffff:127.0.0.1]
Nov 15 14:52:03 mars imapd-ssl: LOGIN, user=rcordeiro, ip=[::ffff:127.0.0.1], protocol=IMAP
Nov 15 14:52:03 mars imapd-ssl: DISCONNECTED, user=rcordeiro, ip=[::ffff:127.0.0.1], headers=0, body=0, time=0, starttls=1