You can use fetchmail or getmail (see http://www.howtoforge.com/debian_etch_fetchmail
). Both pass on the emails to your MTA (Postfix in your case) on port 25.
If you try to send emails from your local mailserver, please keep in mind that dynamic IPs are blacklisted. You should set up relaying then: http://www.howtoforge.com/postfix_re...her_mailserver