Small SMTP Restriction, Big Results
August 11, 2006 · Filed Under Opinions on Email Security
We try various smtp level spam restrictions here with varying results. Here are some of my observations on our efforts.
We highly recommending rejecting non fully-qualified host names. This means that hosts that try SMTP HELO that do not present their fully-qualified name are rejected. This small check will get rid more spam than you’d believe. In postfix this option is configured as:
smtpd_recipient_restrictions =
reject_non_fqdn_hostname,
This can be augemented with reject_non_fqdn_sender which checks mail from: in the SMTP exchange, after the HELO. From: addresses not presented as fully-qualified names will be rejected.
These small tidbits will spare you much spam.
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