Microsoft 365 users cannot log in since upgrade to 3.6. Error: 422. Email address is already used for other user


  • Used Zammad version: 3.6.x
  • Used Zammad installation source: yum -y install zammad
  • Operating system: CentOS Linux release 8.3.2011
  • Browser + version: Latest Chrome, Firefox, Edge

Expected behavior:

Be able to log in using the Office 365 red button.

Actual behavior:

Error: 422. The change you wanted was rejected
Email address xxxx is already used for other user.

Steps to reproduce the behavior:

Everything was working since last update in March 2020.
Ran “yum update” today and now Microsoft 365 users cannot log in with the above error
Local users can log in fine.

I’ll keep investigating and post a solution if I figure it out but if anyone knows a solution please do let me know as I did not find anyone else posting about this issue.

Thank you

The fix for anyone else:

There is a (new?) option in settings - security called: Automatic account link on initial logon
Turn this on and now M365 users that could previously log in can log in again.

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This setting is not new but in general suggested to use normally in those cases.
Note that there was a breaking change with changing UUIDs because of scope changes that probably affect you here.

We pointed that out on the release notes- I’d like to suggest to check them before updating. They may hold crucial information that safe you from crashing into a big wall.

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