Sendmail/Spamassasin/Spam

[Bret Stern]

Hey,

I'm hosted on Verio VPS Red Hat Enterprise 3.

Haven't spent a lot of time with Sendmail, but i'm getting
pissed with all the spam, and probably need a basic understanding
of the mail services.

Using:
Sendmail 8.14.4
SpamAssassin

Can I setup (similar to IPTABLES), reject all mail
except from specific domains using the access db?

I've seen some samples, but not specifically what I want to do....
or is this not a good idea.

As always, thanks.