As for "not doing much work" - it is tougher than you think to make a
useful package that seamlessly integrates all the tools you mention,
plus makes it work as designed, with a user interface that manages
configs seamlessly, etc etc.
There are lots of mailserver + junk filtering appliances like for
example barracuda, that are basically 1U servers running linux +
spamassassin + postfix + a web interface ..
