Outlook IMAP or POP server unexpectedly terminated the connection, and the server was interrupted

Outlook stops connecting to your mail server. You may see errors such as the following:

“The connection to the server was interrupted.”

Task 'User Name - Receiving' reported error (0x800CCC0F) : 'The connection to the server was interrupted. If this problem continues, contact your server administrator or Internet service provider (ISP).'

“Your server unexpectedly terminated the connection. Possible causes include server problems, network problems, or a long period of inactivity.”

STATUS: WORKAROUND

After investigating this further we are seeing two workarounds to help with these errors:

Workaround #1: If you are getting the errors in the section above, it could indicate that there’s a problem with the App Password. This could happen on Windows 10 or Windows 11. To fix the App Password, log in to your IMAP email provider’s web email and go to Account Information > Security and create a new App Password.

To fix the App Password on your email account in Outlook do the following:

1. In Outlook select File, under Account Information click the drop-down and select the IMAP account with the errors above.
2. Select Account Settings >Server Settings.
3. On the IMAP Account Settings paste the new App Password in the Password box.
4. Select Next, then Done.

Workaround #2: We tested further and found that TLS 1.3 may cause the errors above if you are on Windows 10. Our testing found that Windows 11 TLS 1.3 should be working fine with Outlook. If you are on Windows 10, use the steps below to disable TLS 1.3 to address the errors in the article above.

This issue can occur if your machine was updated to have TLS 1.3 configured. To work around the issue, remove the TLS 1.3 settings by doing the following:

1. Click Start, search for Regedit and open the application
2. Navigate to this path in the registry:

1. Review if you see TLS 1.3 under Protocols. If you do, right click on Protocols and click Export to save out a registry export of the configuration in case you need to revert back for any reason.
2. If under Protocols you see TLS 1.3 delete that key and its sub keys.
3. Restart Outlook. If you still don’t see sync start working, restart Windows.

After making the change the registry should appear similar to below not showing any TLS 1.3 keys.

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