Why can’t send message due to error 0x800ccc78?

I’m trying to send a message via Outlook, but it says “unknown error” and code 0x800ccc78? I tried many things, but without success. Any ideas?


Hello! I managed to find one working solution, which, judging by the reviews, works for most users. All you have to do is make one setting. I am attaching the instruction, but the name of the items may differ depending on the version of your Microsoft Outlook.


  1. Go to the “Tools” tab, and then “Email Accounts”.
  2. We select the account with which there are problems, and click on the “Advanced settings” button.
  3. Click on the “Outgoing mail server” button and activate the item “My outgoing mail server requires authentication.”
  4. Activate the “Use the same settings as my incoming mail server” option.
  5. Click on the “OK” button and try to send the letter again.
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