on 09-04-2020 07:34 AM
Your post from earlier seems to have arrived late.
Outlook appears to be set up as an IMAP account which is good. It completes sending your mail message(s) which is good. It then tries to synchronise the mailbox folders on the mail server with Outlook so that you can see those folders on your device. It's reporting (unknown) errors.
Is this a permanent error? If not it could just be a glitch in your broadband / wi-fi connection.
If it is a repeatable consistent error the first fix is to troubleshoot an error in Outlook's files by removing the mail account from Outlook and then reinstating.
If still there it could be an individual mail message in one folder that's corrupted. You could therefore try synchronising to just the Inbox by unticking other folder subscriptions in Outlook.
And then resubscribing to the other mailbox folders in turn to see if you can track down the error.