Is the authentication method in Server Settings OAuth2? Does the error really refer to imap.gmail.server? The correct server is imap.gmail.com on port 993, SSL/TLS security.

Hello sfhowes,

I guess I have been so frustrated with this problem, I forgot one thing and mis-typed another.

The error does refer to "server imap.gmail.com". It is port 993, SSL/TLS. I have OAuth2 in my server settings.

The one thing I forgot was after the update had been applied, the first thing that happened was I was prompted for my Google user id and password sign-on. I entered my password incorrectly 2 times; on the 3rd time it was correct and seemed to be OK. When I clicked "Get Messages", I got the error that this is all about.

I hope this new information is helpful. Thank you.

Go to Options > Saved Passwords and delete all entries for that Gmail account, then check for messages. You will get the prompt for login credentials. Enter full email address and correct password.

Hello Stans,

I really had hope for your solution, but I did what you said and cleared the saved passwords and still got the error message. I even went and changed my Google account password, cleared the Thunderbird saved passwords, clicked "Get messages", entered the userid and new password. No luck, same error.

It's been suggested to me that perhaps still being on Windows 7 is causing my recent software errors. (I've also been having problems with SurfShark VPN and DivX Pro.) I will be updating to Win 10 soon.

Thank you for your help. Cheryl

If you have a VPN active while trying to connect to mail servers, that is a likely source of errors. Disable the VPN and see if that makes a difference.

Hello sfhowes,

My disfunctional VPN has been deactivated most of the time with this problem. I even activated it to see if THAT would help. Haha! Of course, it didn't.

I appreciate the help I have gotten from you and stans. Thank you so much! Cheryl