Spam Filtering with Port Forwarding and Geo-Location

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Revision as of 07:44, 26 February 2010 by Herbison (talk | contribs) (Spam E-Mail Filtering by Geo-location)
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This page is a work in progress (started on February 25, 2010)

The procedures outlined in this document should work with any mail server software.

For several years I have been running a small ISP. We regularly receive approximately 20,000 legit emails per month. We use several servers running postfix and amavisd-new. We have servers setup for our MX Records which forward to our mail storage server. We have been using greylisting (policyd v1) until recently when I concluded that it's effectiveness had diminished significantly.

We recently moved all of our servers behind a trusty power-router (mikrotik x86) firewall and I was determined to find a way to use it effectively. With all of the servers having an internal address scheme, I now have control over which mail server handles incoming mail. To this end I added a couple of extra MX records to our primary domain to fool spammers.

First off I wanted to load balance the inbound mail. So I created the following nat rules:

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