Ralph Fox wrote:
On Fri, 7 Sep 2018 20:23:17 -0400, Big Al wrote:

On 09/07/2018 08:01 PM, Ralph Fox wrote:
On Fri, 7 Sep 2018 16:08:42 -0700, cameo wrote:

One day it popped up a message saying that my Gmail account was not
secure there and offered me a button to click to fix it. So I did click
it and ever since I can't use that email account in Thunderbird. The
worst thing is that I can't even go back to the state before that
security warning. Interestingly, I also have 2 other Gmail accounts
there and they work fine because I did not try to "fix" them.
I tried to remove the failing account and then re-add it to Thunderbird
with the same server settings as the other 2 working accounts, but it is
still a no-go. Any suggestions?

There is a simple fix:
In Thunderbird, change your Gmail account to use OAuth2 authentication.

Here is a screen-shot of the OAuth2 option in Thunderbird.
http://i.imgur.com/dPUg7N3.png

Someone made the comment that OAuth2 only works for IMAP. (Unless TB
added it for pop).

AFAICT OAuth2 works for IMAP and for SMTP, but not for POP.

Indeed it does not work for POP. I saw that your screenshot shows the
'Server Settings' for an IMAP server, so I checked and the IMAP
'Authentication method' can indeed be set to 'OAuth2', but for a POP
server, that setting ('OAuth2') is not available.

If someone wants to POP their Gmail, use a Google app password with
the POP account. A Google app password also meets Gmail's requirements
for not being "less secure".

How do I do that? I don't know what "a Google app password" is (in
this context) and hence not how/where to set one.

Thanks.