Bug: Outlook no longer connects to the mail server (October 2022)

[German]Microsoft confirms another error in Outlook in Microsoft 365 in a support post. It may be that Microsoft Outlook can no longer connect to the email server. The IMAP or POP server has disconnected unexpectedly and the connection to the server has been lost. Error code 0x800CCC0F is reported.


Last Friday, Microsoft (Oct. 5) updated the Outlook issues page in the October 2022 section. In addition to a fix for Outlook crashes (see Microsoft releases fix for Outlook 365 crashes at startup (Oct. 5, 2022)), a connection issue was also documented in the support post Outlook IMAP or POP server unexpectedly terminated the connection, and the server was interrupted

The Outlook connection problem

In the support document, Microsoft writes that Outlook suddenly stops connecting to the email server. You may see errors like the following:

"The connection to the server has been lost."

The 'Username – Receive' task reported the error (0x800CCC0F): 'The connection to the server has been lost. If this problem persists, contact your server administrator or Internet Service Provider (ISP).

Outlook error

"Your server has disconnected unexpectedly.  Possible causes are server problems, network problems, or a long period of inactivity."

Outlook error

Ultimately, the Outlook client can no longer connect to the server. Affected is Outlook for Microsoft 365 on Windows 10 and Windows 11. Microsoft is currently investigating the issue, it might be related to TLS 1.3.


Workarounds should be possible

In the support article, Microsoft suggests two solutions for those affected to fix the problem.

Workaround #1

One workaround would be to make sure that there is no problem with the app password. This may well occur on Windows 10 or Windows 11. To fix a problem with an incorrect password in Outlook, two steps are suggested.

Log in to your IMAP email provider's web email, go to Account Information > Security, and create a new app password.

To change the app password for this email account in Outlook next, do the following:

1. Select the Outlook File menu, click the drop-down menu under Account Information, and select the IMAP account with the above errors.

2. Select Account Settings > Server Settings and in the IMAP account settings, paste the new app password in the Password field.

The last step is to confirm using the Next and then Done buttons.

Workaround #2

Microsoft has found in further testing that TLS 1.3 can cause the above errors on Windows 10 (Windows 11 is not affected). Systems that have been updated to use TLS 1.3 are likely to be affected. If the error occurs in Windows 10, the following steps should be taken to disable TLS 1.3:

1. Start the registry editor regedit.exe via Run as administrator.

2. Then delete the following registry entries.

Navigate to the following path in the registry:


Check if you see TLS 1.3 under Protocols. If yes, export the content of this key as a precaution, e.g. using the command in the File menu or the context menu.

Registry: Protocols entry

Der Export ermöglicht später den Inhalt wieder zu importieren und so den alten Zustand wiederherzustellen. Nach dem Export kann dann der Schlüssel und seine Unterschlüssel für TLS 1.3 unter Protocols gelöscht werden. Im Anschluss ist Outlook neu zu starten. Funktioniert die Synchronisierung immer noch nicht, starten Sie Windows neu.

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7 Responses to Bug: Outlook no longer connects to the mail server (October 2022)

  1. Holdenger says:

    Those workarounds doesn't work. My IMAP/POP3/SMTP server does support TLS1.2, however, Outlook just can't connect to it.

  2. Peter Adamka says:

    remove patches:
    win11: KB5018427
    win10: KB5018410

    • Pavin Joseph says:

      Thanks Peter, removing the update fixed the issue.
      Hope Windows can roll out corrective updates soon.

  3. scott howell says:

    Error code 53003.
    Is this a full system outage?
    Has Gates crossed the line with an interruption of our mass communications just to start something bigger?

  4. Advertising

  5. mallo malli says:

    same problem, on windows 11 with new app outlook preview

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