How to Filter junk by valid accounts

[Carr, Daryl B.]

Hello,

What is the best way to filter email addresses as "valid" with sendmail.
We have recently experienced a large increase in junk email resulting in
the mqueue.in becoming very large (>400,000).

I have investigated LDAP, NIS, lists of names, etc.

Please point me in the best direction.

Thank you!

Daryl

Daryl Carr
Monmouth College
Monmouth, IL USA