The dreaded 0x800CCC0F sending error

Anonymous

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

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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:

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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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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Anonymous

2022-08-06T21:28:46+00:00

It's not attachments. And it's not Outlook. It's a problem with Google Workspace.

I took your advice, and installed emClient; it supports OAUTH, which both GMail and Yahoo support. I configured accounts I have on both, and was successfully able to send emails to both with "test" as the body. I then used "lorem ipsum" text in the attachment as the body of the email; ~32K bytes worth. The email to Yahoo went through; the email to Google Workspace did not. Log snippets below.

I spent several frustrating hours on the phone with Google yesterday, only for them to conclude it was a problem with Outlook, and they wanted logs from me. Well, logs they will get now - this is a smoking gun.

Yahoo:

17:16:54.085|016| eM Client 9.0.1708+2cfb4a5e03 (Windows)

17:16:54.085|016| Account's UID is 0fb5491b-d1b2-4d97-a58a-babfca36c932

17:16:54.085|016| AccountBase.ChangeOnlineState : State changed to ONLINE due User

17:17:24.230|01E| SMTP S: 220 smtp.mail.yahoo.com ESMTP ready

17:17:24.235|01E| SMTP C: EHLO [192.168.1.170]

17:17:24.277|01E| SMTP S: 250-hermes--production-ne1-6649c47445-tp7sw Hello [192.168.1.170] [100.34.152.185])

17:17:24.277|01E| SMTP S: 250-PIPELINING

17:17:24.277|01E| SMTP S: 250-ENHANCEDSTATUSCODES

17:17:24.285|01E| SMTP S: 250-8BITMIME

17:17:24.285|01E| SMTP S: 250-SIZE 41697280

17:17:24.286|01E| SMTP S: 250 AUTH PLAIN LOGIN XOAUTH2 OAUTHBEARER

17:17:24.290|01E| SMTP C: AUTH OAUTHBEARER <Parameter removed for privacy reasons.>

17:17:24.553|01E| SMTP S: 235 2.7.0 Authentication successful

17:17:24.558|01E| SMTP C: MAIL FROM:<******@yahoo.com> SIZE=28978

17:17:24.666|01E| SMTP S: 250 2.1.0 Sender <******@yahoo.com> OK

17:17:24.667|01E| SMTP C: RCPT TO:<******@yahoo.com>

17:17:24.708|01E| SMTP S: 250 2.1.5 Recipient <******@yahoo.com> OK

17:17:24.708|01E| SMTP C: DATA

17:17:24.749|01E| SMTP S: 354 Ok Send data ending with <CRLF>.<CRLF>

17:17:24.758|01E| SMTP C:

17:17:24.758|01E| SMTP C: .

17:17:25.255|01E| SMTP S: 250 OK , completed

17:17:25.258|01E| SMTP C: QUIT

17:17:25.300|01E| SMTP S: 221 Service Closing transmission

Google Workspace:

17:11:18.726|015| eM Client 9.0.1708+2cfb4a5e03 (Windows)

17:11:18.726|015| Account's UID is 1e302ec2-6d7d-4777-b876-5b64f0b9407f

17:11:18.726|015| AccountBase.ChangeOnlineState : State changed to ONLINE due User

17:13:02.680|024| SMTP S: 220 smtp.gmail.com ESMTP y5-20020a37f605000000b006b5f8f32a8fsm5608350qkj.114 - gsmtp

17:13:02.681|024| SMTP C: EHLO [IPv6:2600:4040:7664:500:4d45:15a4:d1a8:daf0]

17:13:02.703|024| SMTP S: 250-smtp.gmail.com at your service, [2600:4040:7664:500:4d45:15a4:d1a8:daf0]

17:13:02.703|024| SMTP S: 250-SIZE 35882577

17:13:02.712|024| SMTP S: 250-8BITMIME

17:13:02.712|024| SMTP S: 250-STARTTLS

17:13:02.712|024| SMTP S: 250-ENHANCEDSTATUSCODES

17:13:02.712|024| SMTP S: 250-PIPELINING

17:13:02.712|024| SMTP S: 250-CHUNKING

17:13:02.712|024| SMTP S: 250 SMTPUTF8

17:13:02.713|024| SMTP C: STARTTLS

17:13:02.732|024| SMTP S: 220 2.0.0 Ready to start TLS

17:13:02.749|024| SMTP C: EHLO [IPv6:2600:4040:7664:500:4d45:15a4:d1a8:daf0]

17:13:02.979|024| SMTP S: 250-smtp.gmail.com at your service, [2600:4040:7664:500:4d45:15a4:d1a8:daf0]

17:13:02.979|024| SMTP S: 250-SIZE 35882577

17:13:02.979|024| SMTP S: 250-8BITMIME

17:13:02.979|024| SMTP S: 250-AUTH LOGIN PLAIN XOAUTH2 PLAIN-CLIENTTOKEN OAUTHBEARER XOAUTH

17:13:02.980|024| SMTP S: 250-ENHANCEDSTATUSCODES

17:13:02.980|024| SMTP S: 250-PIPELINING

17:13:02.980|024| SMTP S: 250-CHUNKING

17:13:02.980|024| SMTP S: 250 SMTPUTF8

17:13:02.980|024| SMTP C: AUTH OAUTHBEARER <Parameter removed for privacy reasons.>

17:13:03.113|024| SMTP S: 235 2.7.0 Accepted

17:13:03.114|024| SMTP C: MAIL FROM:<******@59plymouth.net> SIZE=28958

17:13:03.132|024| SMTP S: 250 2.1.0 OK y5-20020a37f605000000b006b5f8f32a8fsm5608350qkj.114 - gsmtp

17:13:03.132|024| SMTP C: RCPT TO:<******@59plymouth.net>

17:13:03.150|024| SMTP S: 250 2.1.5 OK y5-20020a37f605000000b006b5f8f32a8fsm5608350qkj.114 - gsmtp

17:13:03.150|024| SMTP C: DATA

17:13:03.306|024| SMTP S: 354 Go ahead y5-20020a37f605000000b006b5f8f32a8fsm5608350qkj.114 - gsmtp

17:13:03.310|024| SMTP C:

17:13:03.310|024| SMTP C: .

17:13:22.714|024| Exception: MailClient.Accounts.SocketException: Sending messages failed due to the following reason:

17:13:22.714|024| "Unable to read data from the transport connection: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond.."

17:13:22.714|024| at MailClient.Protocols.Smtp.SmtpSendCommand.Execute(WorkerStatus status)

17:13:22.714|024| at MailClient.Commands.Command.Process(WorkerStatus status)

17:13:22.715|027| AccountBase.ChangeOnlineState : State changed to OFFLINE due BrokenConnection
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Karl Timmermans 3,685 Reputation points Volunteer Moderator

2022-08-05T17:54:54+00:00

I'd be happy to try out any other suggestions that may occur to you in the meantime.

I'd offer other suggestions if I had any. This is the first time I've seen a report about an attachment of 14K or larger running into an issue. That is by no means what would considered a "large" attachment.
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Anonymous

2022-08-05T17:43:17+00:00

Well, things are looking up (I think); I had said

It seems to me: There ought to be some diagnostic tool, that see what is or isn't going out of Outlook, and what is or isn't coming back from Google; and if something does come back, what it is unhappy about besides "the connection was interrupted".

And it turns out there are several; but I found this one to my liking. And, I learned a lot about smtp connections in the process.

Despite Microsoft's disclaimer that the retail version of Outlook 2016 did not require 2SV and an App PW, SMTP Console reported back exactly what GMail was saying: An App PW was required, just as you had recommended at the start of this thread. So I put it back, created a new profile, configured the gmail account to use the App PW, and... voila! I can send email.

...provided the size of any attachment is somewhere south of 14,083 bytes. I created a "lorem ipsum" text file, and the largest I was able to send was 13,363 bytes. And the thing is - the transmission was near instantaneous for any file 13K or less; but at 14K, the "sending message 1 of 1" message hangs around for about 20 seconds, before the dreaded 0x800ccc0f error message. (I had bumped the timeout from 3 to 4 minutes, to no avail; trouble happens in under a minute.)

So the problem has been narrowed down considerably. Time to get on Google's radar again; thanks for all your help, I'd be happy to try out any other suggestions that may occur to you in the meantime.

Dan
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