Tonight I uninstalled Avast to see whether it was causing slowdown issues with my personal home desktop computer (Windows 10, 64-bit). When I did, Outlook 2010 stopped being able to connect to my IMAP profile. It can still send via SMTP but not connect to my IMAP folders. Outlook 2010 gives me an error 0x800CCC0E. What is more strange, the Mail app on Windows 10 can access the same IMAP account and read new messages perfectly fine. I've tried telling Windows Defender not to do a live-scan but this doesn't seem to change anything.
Then I re-installed Avast and instantly Outlook worked again. Uninstalled it again - same problem immediately returned.
My IMAP server requires SSL on port 993, if that is possibly relevant.
This is completely the opposite of what I'd expect... I'd expect the presence of antivirus software to interfere with my emails, not its absence! Any help would be appreciated.