Hi,
Would you recommend it?
Yes, but first choose MTA (postfix, exim..), then amavis-version.
Is it relatively easy to set up?
Depends on mailer. For postfix I would say yes, don't know exim etc. so good.
and a "webmin" front end. The clever thing it does is transparently to capture inbound and outbound SMTP connections, silently forwarding them on, a bit like a proxy server, but then when the actual DATA command comes it pulls aside the email, scans it for viruses, then forwards on the DATA command (and the actual email).
Don't think so, guess they use a MTA which does not change any header. You can do a port redirect with iptables on port 25 on your scanning host, redirecting it into a MTA you configure to resend the stuff after scanning. Usually you will find some headers of that MTA in the mails, but maybe some mailers allow to switch off these manipulations. At last you can "fix" the sources, but I've seen solution with out-of-the-box SuSE doing that stuff nicely (with headers). Ciao, Dieter