SMTPAuthenticationError M365 Channel


  • Used Zammad version: 3.6.0-1611733683.51a3d218.bionic
  • Used Zammad installation type: package
  • Operating system: Ubuntu 18.04.5 LTS
  • Database + version: postgresql 10
  • Elasticsearch version: 7.8.1
  • Browser + version: Firefox, latest; Opera, latest

Expected behavior:

  • successful sending of Emails via M365 Channels

Actual behavior:

  • adding M365 channels works without errors (done by following the zammad docs)
  • receiving emails works (via imap)
  • sending emails fails with error below
    excerpt from production.log:
    ERROR – : Can’t use Channel::Driver::Smtp: #<Net::SMTPAuthenticationError: 451 4.7.0 Temporary server error. Please try again later. PRX4 [PR0P264CA0285.FRAP264.PROD.OUTLOOK.COM]

Steps to reproduce the behavior:

  • Setup M365 channel with Zammad docs

Steps done prior:

  • tried sending with enabled and disabled SMTP AUTH in Exchange Online for relevant channels (same error)
  • successfully reauthenticated the channels
  • checked for authentification errors of the channels in the admin center of M365 (non were shown)
  • checked settings for possible misconfiguration in Exchange Online (is there a checklist, which settings are crucial for communication with Zammad?)

From what I understand is that Zammad uses SMTP port 465 to send emails with TLS. A colleague told me the configuration of our Exchange Online requires SMTP port 587.
I wasn’t able to change the SMTP port for M365 channels on the GUI.
Is the SMTP port already the problem or doesn’t it matter?

If there’s crucial information missing, I’d be happy to provide it.

Any help would be appreciated.

Best regards

Zammad uses the official communicated ports and servers by Microsoft ( POP, IMAP, and SMTP settings - Office Support ) - if you don’t believe me, here’s the proof: zammad/microsoft365.rb at 5df98684da64aed93cc29e4be029d81566520906 · zammad/zammad · GitHub

The error message 451 4.7.0 Temporary server error. Please try again later. PRX4 [PR0P264CA0285.FRAP264.PROD.OUTLOOK.COM] comes directly from Microsoft. Zammad has no power about that at all.

As the error indicates: It’s temporary. In hosted environment we see this once in a while - it solves itself out within 30 minutes usually. All you can do is wait or contact your provider (Microsoft).


sorry for the late reply.

Thank you so much for your time and the link.
Zammad indeed runs like a charm and the issue itself lied within the licensing of Exchange Online.
After contacting the Microsoft Support the issue could be solved.

Best regards

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