Thunderbird IMAP responded: User is authenticated but not connected

Anonymous
2022-12-27T12:29:12+00:00

Since yesterday, my Thunderbird client cannot connect to the outlook.office365.com IMAP server and other users at my university are also having this problem. I have deleted the stored token and redone the connection procedure but it does not work. I get two error messages:

The current operation on 'inbox' did not succeed. The mail server for account ... (IMAP) responded: User is authenticated but not connected.

Server outlook.office365.com has disconnected. The server may have gone down or there may be a network problem.

This does not work on any platform: Windows, Linux or Macos. Via the browser, we can access the emails but it is a workaround because it does not support openPGP. We need Thunderbird

Outlook | Web | Outlook.com | Account management, security, and privacy

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Anonymous
2022-12-28T22:03:29+00:00

Hi Glenn,

Which version of Thunderbird are you using.

I have 102.6.1 which is the latest one. Can you try updating it if its not and then check.

Also under Thunderbird --> Click on the gear icon on the bottom left bar --> General --> Config Editor --> Show All

Type network.dns.dis in the search field

Select the very first option and click on the toggle arrow on the right, make it true

Close and reopen Thunderbird.. See if this helps

Let me know how it goes

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Anonymous
2022-12-28T21:34:14+00:00

Yes, it is worked for me too!

I just disabled ipv6 netwotking in thunderbird advanced configuration editor (network.dns.disableIPv6 = true)

and it is works again like a charm!

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  1. Anonymous
    2022-12-31T17:47:33+00:00

    Just had a user on my tenant report this issue in to me yesterday so pleased I found this thread. I have a few dozen Thunderbird users and he is the only report so far. I use Thunderbird myself and have several system accounts on it and all are working fine for me.

    Do we have any theories as to why some end users would see this and some not? e.g. is it to do with their particular service provider? (accepting the root cause is likely something Microsoft have done).

    As an aside, this isn't the only problem Microsoft have caused with IMAP recently, and impacting Thunderbird and other mail clients. The following issue has been going on for two months and Microsoft still haven't fixed it.

    https://answers.microsoft.com/en-us/msoffice/forum/all/unable-to-subscribe-to-office-365-imap-folders/c9273f2c-b63c-4647-87ce-bab6625814e6

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  2. Anonymous
    2022-12-31T16:28:28+00:00

    Same PC: problem only when connected to an IPv6 net.

    solved with workaround of

    network.dns.ipv4OnlyDomains = office365.com

    forcing TB to connect to 365 with IPv4.

    MS: what did you do?

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  3. Anonymous
    2022-12-31T14:54:42+00:00

    Still broken here (Mac Mailmate client over IMAP to Office 365). Turning off IPv6 workaround works.

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