Mail server setup

[Sarunas Burdulis <sarunas@nospam.net>]

Hello,

I'm looking into setting up a mail server with the following features:

1. Scan mail for virii (using ClamAV).
2. Scan mail for spam (using spamd).
3. Relay using SMTP AUTH for "road warriors" (cram-md5 or plain + SMTP TLS).
4. Authentication using system accounts in /etc/passwd with possibility to switch to LDAP.

I'm currently using sendmail with milters for parts 1 and 2.

So far I only skimmed through Postfix and Exim docs and it's somewhat not that quite clear whether 
the 3+4 part is at all possible. Has anybody done this on Debian?

Thanks,

Sarunas Burdulis