DMARC and Listmail

I have been trying to figure out a problem with MDaemon listmail. Some members don’t see original posts until another member replies to the original post. I have no clue whether this behavior is related to DMARC but I would appreciate any suggestions/recommendations that may help. I have been using DMARC for awhile now with p set to quarantine. Since joining dmarcian I have been implementing policy change. I currently have p=reject and pct=5. The behavior noted above has not changed. My knowledge of DMARC is limited and I am curious how p being set to quarantine or reject would affect the sending of listmail, if any?

Hi mux and welcome to the forums!

A restrictive DMARC policy on a sending domain participating in your list discussion definitely could be rejected or quarantined. It all depends on the sending domain’s policy. This means either when a user sends to a list address, or a member replies to an existing list discussion.

There are 2 options of notes in MDaemon that could impact users with restrictive DMARC policies.

  1. “Refuse messages from domains with restrictive DMARC policies” under Mailing List Settings.
  2. “Replace From email address with list’s email address if message is sent from a domain that publishes restrictive DMARC policy.” found in the Headers screen of the Mailing List section.

To ensure delivery of emails from domains with a restrictive DMARC policy, option #1 needs to be disabled, while option #2 must be enabled.

I would check those options first. If that does not help, then I would imagine DMARC is likely not the culprit. However, a more in depth investigation and reviewing samples of impacted emails would be my recommendation.

I hope this helps!

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