I see that your server have some instructions how to set an email client (like thunderbird). Please check on thunderbird settings if those settings are the same as on those instructions (I am not allowed to post a link here). So you should check pop server, port settings, ssl options (and off-course user and password)

Hello and thank you for responding quickly,

Okay. I just checked and actually it comes from there: In the server settings under Security settings then Connection security choose None (I was under SSL / TLS).

I can now receive my emails without problems.

Thank you anyway.

Subject resolved.

Good afternoon.

I have the same problem, and I have been using Thunderbird for at least 20 years. I am also the office fix-it person, and have had no luck. I have tried all the solutions I have seen on the Support forums and none work.

I can send email, but I cannot receive email. When I click "Get Mail" it tells me "connected to inbound.att.net...." at the bottom of the screen, but it never goes further than that. This happens for all five work emails I have on this computer's Thunderbird.

We reset all the emails to a Secure Email Key through ATT, and they were all working last week. I did remove the saved passwords and get a new key for this week. Thunderbird will not even take me to the "enter password" screen.

I tried resetting the security to None as mentioned above, but it does not solve the problem.

On another thread, it was suggested that I flush the DNS cache which I did successfully, and it had no effect. (https://support.mozilla.org/en-US/questions/1306337)

I have gone through and archived or deleted many old messages, and it had no effect.

I went into the Config Editor and switched a setting from 1 to 3. It had no effect, so I switched it back. (I can't find the original thread, but that was one suggestion.)

I switched off my Webroot security for email, and it had no effect.

There was one additional thread (https://support.mozilla.org/cs/questions/1224977) which suggested to stop indexing to a folder, but I was unclear as to which folder.

Our internet is slow, but it has always been slow, so I do not understand why that would suddenly be an issue. Our office is closed due to COVID and no one is there to reboot the router. I don't want to send anyone in, except as a last resort.

Downgrading TLS min version to 1 (TLS 1.0) did the trick for me. See https://support.mozilla.org/en-US/questions/1314691