SPAM - Linux Postfix

Defending against Spam using Linux Postfix
www.fduran.com

0) Consider outsourcing mail service

1) Spamassassin: good in it's time, it's past its useful life since there are better options and it's a CPU hog.

2) Use black list servers, like Spamhaus and Spamcop:

In Posfix configuration file /etc/postfix/main.cf append:

smtpd_recipient_restrictions = ... reject_rbl_client zen.spamhaus.org reject_rbl_client bl.spamcop.net

This stops most spam before it's processed further by server.

3) If blacklist wasn't enough then you can also use greylisting: http://rimuhosting.com/knowledgebase/linux/mail/greylisting%20with%20postgrey

4) To drop email from domains (or addresses) that are just spamming:

Add them to /etc/postfix/access like:
yahoo.cn DISCARD

Add in /etc/postfix/main.cf smtpd_recipient_restrictions = ... hash:/etc/postfix/access

Run postmap hash:/etc/postfix/access and restart postfix
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Somehow related: to check if your mail server is blaclisted: http://www.mxtoolbox.com/Public/Tools/Blacklists.aspx