Microsoft 365 Channel inbound settings


  • Used Zammad version: 6.2
  • Used Zammad installation type: package
  • Operating system: Ubuntu 23.10 + nginx
  • Browser + version: Edge
  • we have a wildcard-certificate in our domain, which is delivered and is valid until Nov 24

Expected behavior:

  • Mailsetting for M365, it has worked perfectly since the beginning of 2023 until last Thursday January 27th, 2024

Actual behavior:


Steps to reproduce the behavior:

  • every time i open Microsoft 365 Channel

Hi @OLB. I guess you need to add your certificate in Zammad: click

If this is the official “” endpoint failing with a self signed certificate error, I’d have serious questions. Make sure you have no application aware firewall that plays man in the middle replacing certificates.

1 Like

Thanks for your reply, but my certificate is installed:

Thanks for the feedback, we have a Firewall (sophos) but it delivers the same certificate.

The main question is: What happened on 27th of January? You wrote that it worked before, so I guess the issue is in the environment, not in Zammad.

Maybe, we have autoupdate for Ubuntu. This makes me wonder: “certificate verify failed (self signed certificate in certificate chain)” is not part of your certificate chain and thus you cannot install an certificate for it. If you did, this might be the root of the issue. Just might.