Email filtering is an essential task. There are many methods like:
=> Bayesian spam filtering
=> SpamAssassin/DSPAM programs
=> Check open relay using RBL etc
Now ORDB.org is shutting down its operation. ORDB is quite effective and I use this list against all of email servers. Spammers still use 3rd party servers and desktop computers so that they could minimize or avoid detection by re-routing their e-mail through these third party e-mail servers.
According to their home page:
We encourage system owners to remove ORDB checks from their mailers immediately and start investigating alternative methods of spam filtering. We recommend a combination involving greylisting and content-based analysis (such as the dspam project, bmf or Spam Assassin). DNS and the mailing lists will vanish today, December 18, 2006.
Generally, I use following sequence while configuring anti-spam
These services blocks thousands of spam everyday before hitting email server and Spam Assassin. Indeed a bad news for mail server admins!