Postfix 2.5.5 SpamAssassin 3.2.5 (under Perl 5.10.0) ClamAV 0.95.1 Dovecot 1.2.rc2
works fine on Fedora 10.
Installed Dovecot and ClamAV from source and everything else using yum.
I'm using the ClamAV plugin for Spamassassin: http://wiki.apache.org/spamassassin/ClamAVPlugin
I'm calling Spamassassin with:
/etc/postfix/main.cf: mailbox_command = /usr/bin/spamc -f -e /usr/local/libexec/dovecot/deliver
Postfix hands off to Spamassassin, which processes ALL mail (not just attachments) through the ClamAV plugin before parsing for spam, and then hands the whole mess off to Dovecot for 'deliver' to handle.
How simple is that?
Since ClamAV scanns all mail, it might be too processor-intensive for really large mail systems, but it is working great for our 120+ user system with lots of spam coming in. If you're using Procmail or some other preprocessor that can hand off to a pipe, then you could skip the plugin and pipe messages over a certain size (i.e. >1024) to clamd, instead.
Enjoy!
James