The dreaded 0x800CCC0F sending error

Anonymous
2022-07-21T19:36:33+00:00

I am now running Microsoft® Outlook® 2016 MSO (Version 2206 Build 16.0.15330.20260) 64-bit, on Windows 8.1; I had been running the 32-bit version, but I upgraded to 64-bit in an attempt to resolve this error on sending: "Task '[email account] - Sending' reported error (0x800CCC0F): 'The connection to the server was interrupted....' "

My Outlook is configured for two IMAP accounts, both with Google - one is a GMail account, the other is Google Workspace account that services email for my domain (59plymouth.net). Outlook is also configured for a work Exchange account.

A few weeks ago - not sure, but I think after a reboot, and when Windows updates were applied - both IMAP accounts stopped sending. The Exchange account continues to work without issue.

The updates were July updates - 5015874, 50156268, and 50154633. Suspecting these, I backed them out and disabled updates. No luck. I then did the Outlook 64-bit upgrade. NADA.

I'd suspect Google, but my iPhone continues to work without issue for both accounts; so does my iPad (which also talks to my Exchange account).

I'm not sure where to go from here. And ideas about how to further diagnose?

adTHANKSvance,

Dan

Outlook | Windows | Classic Outlook for Windows | For business

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  1. Karl Timmermans 3,685 Reputation points Volunteer Moderator
    2022-08-06T21:49:20+00:00

    Well, logs they will get now - this is a smoking gun.

    Hopefully something productive will come out of it.

    Still would have been interesting to know if this is specific to '2016 or Outlook in general.. As previously mentioned, '2016 mainstream support ended Oct '2020.

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  2. Anonymous
    2022-09-30T14:00:27+00:00

    I have been going back through some reports with the errors:

    “The connection to the server was interrupted.”

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

    One cause I found is if TLS 1.3 got configured on the machine. I am working on a Known Issue to document it but sharing here in case it can help. I don't know yet what is setting this regkey.

    1. This issue will occur if your machine was updated to have TLS 1.3 configured.  To workaround the issue do the following:
    2. Click Start, search for Regedit and open the application
    3. Navigate to this path in the registry: Computer\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocol
    4. Before you make any change, right click on the Protocols key and Export it for a backup just in case.
    5. If under Protocols you see TLS 1.3 delete that key and its sub keys.

    This is how it should look from my Win11 computer:

    Image

    Here are a couple other forum threads where they had the same issue for more context and other investigation steps:

    Outlook 2016 connectivity to gmail lost suddenly and cannot figure out - Microsoft Community

    Outlook Cannot Send Emails to Certain Accounts - Microsoft Community

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