Azure OAuth Error 422 - Email has already been taken

A user is having problems logging in, and is getting the error message described above. Neither API or Rails returns any overlap in registered emails on different users, this email is exclusively registered to one user.

Any idea on what might be the issue here?

Error message from GitLab Rails Application log is:

(OAuth) Error saving user <UUID> (<>): [\"Email has already been taken\"]

Just a wild hare thought here… Check the “email” being passed by Azure, are there any weird special characters in it? We had an Azure situation where it added #EXT# to some email addresses and that caused issues for SAML config.

I can’t find in my notes to confirm that was a gitlab issue or some other app using SAML…

Thanks for the tip! There was no additional characters in the email, it looked like a completely normal email address. That said, I will keep this in mind as some users are seldom working in GitLab and there used to be an EXT domain where your example could be applicable.