We have DKIM configured with the MTA we are using with CiviCRM, and it appears to be working. However, the DKIM signature fails consistently; using a checker it appears the mail has been altered after being signed. Has anyone else experience of this?

I've done some more investigation. I have an IIS based development system. Configuring SMTP leads to the test email failing DKIM. Sending a CiviMail test environment passes DKIM. Sending a CiviMail test from Linux Apache based test environment leads to a DKIM failure. Webmail and Thunderbird SMTP both lead to DKIM passes. Any suggestions?

  • Do you have a relay for outbound, i.e. your MTA just forwards to the actual outbound server? Is the FROM getting rewritten? If you send an email through the same MTA with the same FROM but not through CiviCRM, does it pass?
    – Demerit
    Jul 22, 2018 at 19:21
  • We just do a mail() or SMTP connection to our MTA.CiviCRM 5.3.1 appears to replace the From address with the Return-Path address. Sending emails from the MTA's webmail or via IMAP from Thunderbird pass DKIM Jul 23, 2018 at 15:53

1 Answer 1


We did experience that for specific mail providers. Local delivery and most mail providers were fine or not having any non 7bit encoded characters.

We ended up forcing a downconversion to 7bit encoding on our MTA prior to signing with DKIM as described here for postfix: http://postfix.1071664.n5.nabble.com/On-DKIM-and-Content-Transfer-Encoding-tp68767p68769.html

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