This morning I was not able to retrieve email from a POP3 server or from GMAIL using IMAP using latest Thunderbird 78.5.0 on windows 10. I initially thought it was Thunderbird but was told to try disabling the POP3 Scanner setup, which got around the problem. The IMAP problem was very intermittent until I disabled the IMAP Scanner setup in NOD32. Then it worked without issue.
Checked the root cert in ESET and it says OK.
Last night the detection engine updates 22403-22405 were downloaded. I believe after that, I was not able to filter POP3 or IMAP anymore.
I opened a ticket for POP3. I did not open one for IMAP yet.