Mail Server Architecture

["L. V. Lammert" <lvl_(_at_)_omnitec_(_dot_)_net>]

We're planning on upgrading some mail servers with 3.7, .. but we're having 
an internal 'debate' over the architecture.

Keeping things simple (sendmail - don't need antoher MTA debate!), the 
question is three-fold:

1) Vilter/Milter - using sendmail to scan incoming messages in realtime.

    Pro: 	Reject messages before being accepted.
    Con: 	Possibility of locking up sendmail daemon; performance hit for 
large messages.

2) Mainscanner - passing emails to external programs for scanning virus/spam.

    Pro:	Can be restarted automatically if a scan crashes.
    Con:	Messages are accepted even if invalid.

3) Amavisd - alternative to Mainscanner, same architecture

4) Cyrus - doesn't seem to be a package nor complete port in the tree?

There are a variety of notes available, but not a lot of good information 
about *why*. Prefer to stay with sendmail as it's in the base install, and 
we have used SM/MS/ClamAV/SA in the past with some success so there's a 
little intertia towards that solution.

Any pointers to good resources for details would be greatly appreciated.

	Lee