Your settings look good. Are you trying the automatic account configuration?

Then try to use the manual setup instead, and enter the server settings manually.

https://support.mozillamessaging.com/en-US/kb/manual-account-configuration

Just for the records, there are the required AT&T settings.

http://www.att.com/esupport/article.jsp?sid=KB401570&cv=804&title=Email%20server%20settings%20%28POP%20and%20SMTP%29#fbid=UvF_IHcDpcG

I first tried using the automatic account configuration. That didn't work, so I tried the manual setup. I have tried several other configurations that others have recommeded, based on their problems configuring Thunderbird with AT&T. None of these solutions have worked for me. Thanks for providing the link to the required AT&T setting, but I already reviewed that before contacting you for help. This is something that should be simple. I have researched this to death on the internet. Do you have any other ideas on how to resolve this issue?

Thanks, Mark

Check your firewall settings and make sure Thunderbird isn't blocked.

The Windows firewall is turned off. I'm able to ping the inbound and outbound servers. (see below).

U:\>ping inbound.att.net

Pinging pop-secure-att.mail.am0.yahoodns.net [98.138.13.170] with 32 bytes of da ta: Reply from 98.138.13.170: bytes=32 time=73ms TTL=42 Reply from 98.138.13.170: bytes=32 time=72ms TTL=42 Reply from 98.138.13.170: bytes=32 time=72ms TTL=42 Reply from 98.138.13.170: bytes=32 time=66ms TTL=42

Ping statistics for 98.138.13.170:

   Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),

Approximate round trip times in milli-seconds:

   Minimum = 66ms, Maximum = 73ms, Average = 70ms

U:\>ping outbound.att.net

Pinging smtp.att.mail.fy4.b.yahoo.com [67.195.15.5] with 32 bytes of data: Reply from 67.195.15.5: bytes=32 time=119ms TTL=42 Reply from 67.195.15.5: bytes=32 time=119ms TTL=42 Reply from 67.195.15.5: bytes=32 time=119ms TTL=42 Reply from 67.195.15.5: bytes=32 time=119ms TTL=42

Ping statistics for 67.195.15.5:

   Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),

Approximate round trip times in milli-seconds:

   Minimum = 119ms, Maximum = 119ms, Average = 119ms

Using the manual setup, were you able to create the account?

When checking for new mail, what error message do you get?

I was able to create the account, because I've gone back several times to edit it with different entries for Server Settings and Outgoing Server (SMTP). When I click on <Read messages>, it will show "Connecting to inbound.att.net" along with a green progress bar at the bottom of the screen. It eventually times out and goes away, but an error message is not issued.

What other security s/w and/or anti-virus s/w do you have installed?

I am on a business computer, but I have administrative rights on it. I've never had a problem installing any other software. We do run TREND Micro on our network based Exchange server. It should not have an impact on using Thunderbird with my AT&T account. You have been very diligent and responsive to this issue, and I don't want to waste your time. I will be going home in about 30 minutes. I will reinstall Thunderbird on my home computer and see if I still have an issue connecting to AT&T. Please leave this problem open. I will provide you with an update later today after the home install.

Thanks, Mark

When you try to access AT&T servers from a corporate network, the ports for POP and SMTP may be blocked. And I guess you'll have to configure a proxy for your web browser.

So you'd need to talk to your IT folks for clarification.

I was able to get Thunderbird to work with AT&T on my home computer, so there must be a firewall restriction at work. I'm closing this incident.

Thanks very much for your help.

Regards, Mark