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
    2023-01-12T22:52:39+00:00

    Been told by Microsoft today if I want an RCA, I'd have to raise a Premier Support Case - and I have no intention of doing so when this is clearly a bug or config error in key functionality of the Exchange Online service and evidently affecting many customers across Europe.

    The tenant I look after is a non-profit plan offered to charities and the like, so I would never expect anything more than the most basic of service offerings, but this was still a bit of a shocker. If anyone else with deeper corporate pockets, or more comprehensive service plans, wants to try and extract an answer, good luck! :)

    Thanks again to the folks who posted the two variants of IPv4 workaround on here.

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  2. Anonymous
    2023-01-30T03:53:05+00:00

    I had set to network.dns.disableIPv6 = true, but still not work for me. can you share the the TB configuration for IMAP ?

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  3. Anonymous
    2023-01-30T09:59:14+00:00

    I had set to network.dns.disableIPv6 = true, but still not work for me. can you share the the TB configuration for IMAP ?

    Do you mean you set network.dns.disableIPv6 = true and it didn't work with that setting (suggesting you might have a different problem) OR it did work, but setting it back to FALSE after the issue appeared to be resolved earlier this month doesn't work? If the latter, then you will likely need to ask your mail administrator to raise with Microsoft as it appears to be resolved for the rest of us. In any case, these are the IMAP (incoming mail) and the SMTP (outgoing mail) settings you need for Thunderbird when accessing an O365 mailbox. User Name will be your own email address.

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