FC3 Mail Server Spam Assassin

[Bob Chiodini]

How should I set up SPAM Assassin/sendmail to filter email for all
users?

I have FC3 running fetchmail and Cyrus IMAP for my family and noticed
that only the mail read by Evolution passes through spamd.  The kids and
the wife use Thunderbird and Outlook Express on windows. Their email
apparently does not run through spamd.

I'm guessing MIMEDefang as a sendmail milter.  Is the the accepted
method?  Could it be done with sieve?

Bob...