Unable to subscribe to Office 365 IMAP folders from MUA since 2022-11-01

Anonymous
2022-11-02T07:33:01+00:00

I'm using Thunderbird to access my Office 365 mail account and it has been working fine (a couple of month ago I also switched to OAuth2 due to deprecation of basic IMAP authentication). However, since 2022-11-01, Thunderbird is unable to subscribe to IMAP folders. Last time I know it was working was last Friday 2022-10-28. Thunderbird is able to list to available folders (e.g. when opening the "Subscribe" dialog from the mail account settings), but cannot subscribe to them. I enabled IMAP logging in Thunderbird, and it shows that the server answer the subscribe request with "BAD SUBSCRIBE".

It is not a password/authentication issue, as Thunderbird can still see the content of "Inbox" and "Deleted Items". And if I disable the option "Show only subscribed folders", it can access everything in my Office 265 account.

Edit: here's the relevant logs from Thunderbird (note: I've replaced the actual folder name with "xxxx"):

[Parent ...: IMAP]: I/IMAP ...:outlook.office365.com:A:SendData: 76 subscribe "INBOX/xxxx"

[Parent ...: IMAP]: I/IMAP ...:outlook.office365.com:A:CreateNewLineFromSocket: 76 BAD SUBSCRIBE failed.
Microsoft 365 and Office | Subscription, account, billing | For business | Other

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  1. Anonymous
    2022-12-05T12:49:07+00:00

    Not a situation I've personally seen. Are all three accounts on the same tenant just out of curiosity?

    No, three different tenants. (I work as a consultant and these are three different clients.)

    I have no admin access to any of these, so it is limited what I can check / test. The accounts are (were) set up with the same parameters on my side.

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  2. Anonymous
    2022-12-05T12:22:00+00:00

    Not a situation I've personally seen. Are all three accounts on the same tenant just out of curiosity?

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  3. Anonymous
    2022-12-05T11:45:05+00:00

    The only clear and verified pattern I have actually seen to this is the one I noted early on in this thread and fed back to Microsoft. i.e.

    My AFFECTED accounts were all being accessed via IMAP at the time the fault materialised.

    My WORKING accounts* had never been accessed with IMAP before, and were added to mail clients AFTER the fault materialised by way of testing.

    I have three different O365 accounts, and I have been using all three with IMAP & OAuth2 (Thunderbird on Linux) for over a year. Now two of them are affected by this issue, while the third one is still working fine. No idea what the difference is between the working account and the affected ones.

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  4. Anonymous
    2022-12-05T08:37:06+00:00

    It does tend to point that way, but my money is on some deep and obscure infrastructure issue.

    When I set a new user up in O365, it's literally a one minute job. You just assign what O365 services the user has (Exchange online etc.) and that's it. There is virtually nothing you can change config wise or would want to. I've looked for patterns in the way affected/unaffected accounts are setup and found absolutely nothing so far.

    The only clear and verified pattern I have actually seen to this is the one I noted early on in this thread and fed back to Microsoft. i.e.

    My AFFECTED accounts were all being accessed via IMAP at the time the fault materialised.

    My WORKING accounts* had never been accessed with IMAP before, and were added to mail clients AFTER the fault materialised by way of testing.

    *These were in fact some test accounts of mine, but they have been setup for years, and are identical in setup to all other user accounts.

    I originally assumed that this was some glitch and if I could find a way of resetting the IMAP interface on an affected account, it would spring back into life. As an administrator, I can turn IMAP off/on for an individual user account - so I tried that on one of my affected accounts and it made no difference.

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  5. Anonymous
    2022-12-04T23:36:36+00:00

    Thank you for clarifying.

    Seeing that the server response is the same for affected and unaffected accounts, this points towards an account-specific configuration file issue, doesn't it?

    I am not sure how this is implemented on the server side though.

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