Postfix greylisting
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On a lark, I decided to implement greylisting on my mail server. It was as easy as "apt-get install postgrey". Well, almost that easy. I also had to add this to my /etc/postfix/main.cf:
check_policy_service inet:127.0.0.1:60000
This was slipped in at the end of smtpd_recipient_restrictions.
update Now postgrey is running on port 10023, so that line is now
check_policy_service inet:127.0.0.1:10023
The full smtpd_recipient_restrictions looks like this: <pre> smtpd_recipient_restrictions = reject_invalid_hostname, reject_non_fqdn_hostname, reject_non_fqdn_sender, reject_non_fqdn_recipient, reject_unknown_sender_domain, reject_unknown_recipient_domain, reject_unauth_pipelining, permit_mynetworks, permit_sasl_authenticated, reject_unauth_destination, check_policy_service inet:127.0.0.1:10023, check_policy_service unix:private/policy-spf </pre>
Now I have a new service in /etc/init.d: postgrey
Every attempt to deliver mail to my server generates a to, from, sending-host triplet and the request is bounced. After 5 minutes, any requests bearing that same triplet are allowed. After 5 successful mails are sent associated with a single triplet it is whitelisted.
And my logs look like this: <pre> Oct 17 16:16:32 localhost postfix/smtpd[32484]: connect from unknown[201.226.226.55] Oct 17 16:16:35 localhost postfix/smtpd[32484]: NOQUEUE: reject: RCPT from unknown[201.226.226.55]: 450 <rday@finninday.net>: Recipient address rejected: Greylisted for 300 seconds (see http://isg.ee.ethz.ch/tools/postgrey/help/finninday.net.html); from=<lingrossfastenrathmet@grossfastenrath.de> to=<rday@finninday.net> proto=ESMTP helo=<auditoria01.cwpanama.net> Oct 17 16:16:35 localhost postfix/smtpd[32484]: lost connection after DATA from unknown[201.226.226.55] Oct 17 16:16:35 localhost postfix/smtpd[32484]: disconnect from unknown[201.226.226.55] </pre>
My Bayes filter might get rusty from lack of use now. Hardly anything is persistent enough to get through the greylist.
