Do I need SpamAssassin?

[Peter Bonivart]

As I understand it MS checks for spam with help from databases, it also
uses blacklists and whitelists. Detected spam can be marked and
delivered or deleted. Am I right so far?

I would like to keep it simple so what do I need SA for? It's more
"advanced" but what does it mean to me? Will I get a lot of spam without
it? Is it worth the added complexity?

Also, the mail system I want MS in uses Exchange on the inside and they
have anti-virus scanners for that database and also on every desktop.

Is there any point for me to scan mail for viruses at the MTA (Sendmail)
level as well? Isn't the virus scan more resource demanding than the
spam and attachment checks? I'm running Solaris and not all companies
offer scanners for that platform. Any advice?

Sorry for all the newbie questions but I'm really interested in using
this. I have a chance of replacing a commercial Windows-based system
that costs $20.000 a year in licensing alone and I really want to show
what open source can do but this is new to me so I need help. Thanks.

/Peter Bonivart

--Unix lovers do it in the Sun