Recommended Mailing List settings to mitigate DMARC policy (AOL-Yahoo and domains with strict DMARC policies)
Since 2014 Yahoo and AOL (and soon others) have implemented a strict DMARC policy that cause posts from Yahoo/AOL users to be bounced by many other services.
These bounces affect the other recipients of your list: they can be removed while the offending Yahoo or AOL member is left alone.
As of Mailman 2.1.18 and later you have the ability to mitigate this problem.
Here are our suggested settings
Login to your list administration area, then:
General Options Area:
- Replace the From: header address with the list's posting address to mitigate issues stemming from the original From: domain's DMARC or similar policies. - NO
- Hide the sender of a message, replacing it with the list address (Removes From, Sender and Reply-To fields) = NO
Privacy Options>Sender Filters Area:
- Action to take when anyone posts to the list from a domain with a DMARC Reject/Quarantine Policy = Munge From
- Shall the above dmarc_moderation_action apply to messages From: domains with DMARC p=quarantine as well as p=reject = YES