Enforcing more strict anti-spam rules on beastie.frontfree.net
I have turned on several anti-spam settings on beastie.frontfree.net to ease my life. They stand for “most evident spam characters” and hence should not go to the content filtering subsystem and should be directly dropped.
Inspired by OpenBSD’s spamd, I have decided to convert several 550 errors to 450 errors. This forces the spam senders to keep the mail in their sending queue and hence a waste of their resource. (550 means reject permently and hence the sender can drop the mail, and 450 means here is a temporary problem and sender shoud keep the mail for 4 days.)
Among other constrains, here are the most important rules I have applied today:
o When authenticated, you must use your own mail address. Likewise, if a mail claims that is from a user here, they must be authenticated first.
o As an unauthenticated user, the EHLO or HELO must supply FQDN.
o The FQDN must be resolvable.
o Certain addresses could not appear as “sender”, as they doesn’t exist at all.
o Some of my blacklists are imported to postfix’s access databases.