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
    2023-01-03T04:58:10+00:00

    You don't need to globally disable IPv6 in your Thunderbird config, just add office365.com to network.dns.ipv4OnlyDomains

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  2. Anonymous
    2023-01-03T04:55:25+00:00

    Yes, since Christmas, it seems that a range of clients can't receive MS Outlook mail via IPv6. It's not just Thunderbird. Regarding the workaround posted here, you really don't need to globally disable IPv6 in your Thunderbird config. Just add office365.com to network.dns.ipv4OnlyDomains.

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  3. Anonymous
    2023-01-02T23:07:52+00:00

    Thanks for your suggestion, AnkurSrivastava_3010.

    It worked for me and my Thunderbird (version 102.6.1) is now downloading the messages from office365 again.

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