wiki:strict-dmarc-strategy

Version 4 (modified by Jamie McClelland, 5 years ago) (diff)

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Strict DMARC strategy

Yahoo is asking email providers to use strict alignment when evaluating DMARC policies for email messages claiming to be from Yahoo (see our general FAQ for more information).

This page describes our technical approach to addressing this problem.

Our mailing list software relays all mail to dedicated email relay machines (see our bulk mail relay page for details on how that system operates).

Through our puppet configuration (modules/mayfirst/manifests/postfix.pp), our bulk mail relay machines use Postfix header checks to replace the From: line from any email message that is from a yahoo account to a custom address. Here's the regular expression:

/From: (.*<?.*@yahoo\.com(\.[a-z][a-z])?>?)/ REPLACE From: "$1 (Relayed)" <strict-dmarc@mayfirst.org>

The custom address has an auto-responder that refers people to our general FAQ on this topic.

The result is that any email messages from a Yahoo email account that is sent via a machine that uses our bulk email relay infrastructure will have the From address re-written to be from generic address.