SpamAssassin will use tests to check mail headers, the body, IP Addresses and checksums to locate patterns that indicate SPAM.  So SpamAssassin will use pattern-based scores for checking patters that are found in headers, the body or attachments and it will use network-based tests that use DNS lookups or access RBL lists. If you look in the /usr/share/spamassassin directory you will see a list of the tests that are performed by SpamAssassin. The ...

One way you may choose to manage the mail that comes to the Postfix server is to use the locales which is a part of Spamassassin.  If you cannot read other languages there is really no need to run them through your mail system.  So for example if you wanted to limit email to English you would edit the: /etc/mail/spamassassin/local.cf ok_locales             en This will treat any mail in character sets other than Western as spam. ...

Address Sender Verification One of the best methods of restricting SPAM is to require address verification. This means that Postfix will initiate a SMTP session with the client's server to verify that it is a legitimate address. This takes time and resources but...it a very effective way to deal with SPAM. You will need to add the ...

Using a Blackhole The one thing that is important to understand when using blackholes is that these DNS blacklists require Postfix to do a DNS lookup which will take resources from your server and create latency. However, this can be a significant reduction in SPAM. In the example below two kinds of lists are used to block spam, these ...

Non-Routable Networks Spammers will also use networks which are not routeable, thus not traceable. You can stop this technique with Postfix, however, your network firewall should not allow these kinds of networks to enter your network at all. Step #1: Create bogus_mx Create a map that will list these unrouteable networks. Place one ...