Thunderbird IMAP responded: User is authenticated but not connected

Question

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

Answer 1

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

Answer 2

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!

Answer 3

My issue solved by disabling IPv6 from windows network.

Answer 4

dear AnkurSrivastava,

where is this switch to "modern authentication" documented? if you are referring to the switch to oauth2, thunderbird supports that (one of the very few (if not the only) libre mail apps that makes this work with outlook.office365.com).

i've been able to use mfa authentication with thunderbird to connect to outlook.office365.com since i switched to thunderbird 15 months ago when my organization turned on mfa authentication for nearly everything including email.

best wishes,

joe

Answer 5

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

Hey Juan

This is taking place as a result of Microsoft turning on Modern Authentication and enabled security defaults, both of which forbid earlier client apps, such as Office 2013, from being maintained because they now demand modern authentication. Office 2016 is also no longer supported.

In order to utilize Thunderbird, you must connect into Azure and disable the security defaults if you are the organization's IT administrator and oversee Office 365. Disable Modern authentication as well.

Additionally, make sure that SMTP authentication is enabled and turned on for each and every mailbox by visiting their account.

Additionally, Thunderbird won't function if MFA is configured for users because that calls for the new MS Outlook App.

You may easily install the new Outlook if your company uses M365 Apps for Enterprise by heading to Office Portaland selecting "install office."

If this is helpful, let me know.