day 5, still can't send or retrieve. Changed my password 4 times, deleted global-database x million, done this that and the other and still nothing. I can get email via web-base email but not Thunderbird. Any ideas.. anyone?...

Mail server inbound.att.net responded: Server error

I'd suggest you contact your email provider. This looks like a problem at their end.

Changed my password 4 times, deleted global-database x million,

I don't see how this helps with the problem at hand.

Another thing you can try: Try to start Windows in safe mode with networking enabled. - Win10 https://support.microsoft.com/en-us/help/12376/windows-10-start-your-pc-in-safe-mode - Win8 https://support.microsoft.com/en-us/help/17076/windows-8-startup-settings-safe-mode - Win7 https://support.microsoft.com/en-us/help/17419/windows-7-advanced-startup-options-safe-mode#start-computer-safe-mode=windows-7

Still in Windows safe mode, start Thunderbird in safe mode. - https://support.mozilla.org/kb/safe-mode

Does the problem go away?

Windows safe mode disables anti-virus software, which is often the culprit.

Have you created a secure key like your provider seems to require these days? https://www.att.com/esupport/article.html#!/email-support/KM1240308?gsi=0l8785

In the past changing the password has helped within 2-4 hours (this happens 1 or 2 times a year). Can't talk to provider, they don't support or discuss third party software, they'll just suggest I use web-base email, which I hate. And I'm mac not windows. Don't think you read my thread closely there Christ1... must be fog in your office. )

christ1 said

Mail server inbound.att.net responded: Server error

I'd suggest you contact your email provider. This looks like a problem at their end.

Changed my password 4 times, deleted global-database x million,

I don't see how this helps with the problem at hand.

Another thing you can try: Try to start Windows in safe mode with networking enabled. - Win10 https://support.microsoft.com/en-us/help/12376/windows-10-start-your-pc-in-safe-mode - Win8 https://support.microsoft.com/en-us/help/17076/windows-8-startup-settings-safe-mode - Win7 https://support.microsoft.com/en-us/help/17419/windows-7-advanced-startup-options-safe-mode#start-computer-safe-mode=windows-7

Still in Windows safe mode, start Thunderbird in safe mode. - https://support.mozilla.org/kb/safe-mode

Does the problem go away?

Windows safe mode disables anti-virus software, which is often the culprit.

FWIW, I always google the error message. Doing so for this one shows a bunch of hits. So, this is a common problem with this provider (or the provider is enormous, or both).

This post, for example, sounds like your problem. It resolved itself: https://support.mozilla.org/en-US/questions/1226715

This post (also referenced above, but it's very long): https://forums.att.com/t5/AT-T-Internet-Email-Security/inbound-att-net-is-not-responding/td-p/5392045/page/8 suggests that another user found that there was a single email that caused TB not to retrieve email. He solved his problem by deleting the account and recreating it, which triggered allthe email to download but the downlaod stopped on one email. He used webmail to delete that email and the rest downloaded fine. He concluded that that email was malformed.

Obviously, YMMV. Sounds like the main thing you need is a new provider.