- http://spamassassin.apache.org/
- https://en.wikipedia.org/wiki/Apache_SpamAssassin
- https://cwiki.apache.org/confluence/display/SPAMASSASSIN/UsedViaProcmail
- https://wiki.hostsharing.net/index.php?title=Procmail
- https://wiki.hostsharing.net/index.php?title=Spamfilter
- https://www.hostsharing.net/features/spamassassin/