Microsoft 365 Email not working

Hello,

We have built a flow and there the connection with Microsoft 365 worked without problems. Now we want to make the whole thing productive and have to fight with an error that only occurs in the Microsoft 365 Mail module but not with the Excel module.

In Watch Emails, a strange mailbox is now selected at the beginning, but the folder structure is not available:
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The rights to access the mail via the oauth were successfully given, yet the process does not work.

Are there any settings that we may need to make specific to the mailbox (since it worked with another one)?