I recently needed to setup a bunch of new windows 10 laptops with office 365, mainly for outlook to connect to an external IMAP/SMTP server.
Nothing unordinary but on each machine all would connect to and receive email fine but every time it would try to send a test email i would end up with an “Unknown error code: 0x800cce05“.
So i’d skip the test mail, try to send an email and they would just get stuck in the outbox.
After a bit of googling it seemed like a few other people had encountered the same issue. Something to do with corrupt files on the system, i wasn’t sure how this could be on a brand new laptop but i gave it a shot anyway and it seemed to fix the issue.
Close down outlook
cmd as administrator
Open up outlook and all the messages stuck in the inbox should now be sent