Spam filtering using DNS Black Lists
Black lists can be used to filter incoming emails and reduce the amount of spam you receive.
Here is a list of the most commonly used DNS Black Lists
Spamcop DSBL Open relay database Composite blocking list SORBS Spamhaus
Before you start rejecting emails, I strongly suggest that you monitor the email first to get an feel for what you are blocking.
Warning: I do NOT recommend using SORBS, as I have found that Sorbs gives a large number of false positives, and will often blacklist legitimate emails; they way they detect dynamic IP addresses in particular means a domain can be marked as blacklisted even they have done nothing wrong.
Overall, I have found SpamCop to be the most reliable.
