If you are using ESET/NOD32 security/AV then probability is very high it is causing your problems. According to their forums, you should temporarily disable SSL until they solve the problem per https://support.eset.com/en/kb3126-disable-ssl-filtering-in-eset-windows-products?ref=esf - the problem is being reported by dozens of users https://forum.eset.com/topic/26517-problems-with-thunderbird-and-imaps/ https://forum.eset.com/discover/

If you are not using ESET, which antivirus are you using? And what is your recent thunderbird update history according to help > troubleshooting > show update history ?

If you are using ESET/NOD32 security/AV then probability is very high it is causing your problems. According to their forums, you should temporarily disable SSL until they solve the problem per https://support.eset.com/en/kb3126-disable-ssl-filtering-in-eset-windows-products?ref=esf - the problem is being reported by dozens of users https://forum.eset.com/topic/26517-problems-with-thunderbird-and-imaps/ https://forum.eset.com/discover/

Thanks for your prompt reply. I am only using windows installed virus and firewall protection. Not sure if this matters.

re: There was an update and the emails vanished. Now, there are choices to "Read messages" "Write a new message" " Search messages" etc....

That sounds like you have selected the mail account name in the Folder Pane. On the left side of that mail account name, is there a right pointing chevron which indicates there are folders? Can you see folders?

Is this an imap mail account ? If yes, try to subscribe again to see folders. Right click on the mail account name folder in Folder Pane and select 'Subscribe' click on 'Refresh' select all required folders click on 'Subscribe' click on OK

If you can see the folders but no emails:

• Right click on folder and select 'Properties'
• Click on 'Repair Folder'
• click on OK