Bare with me, there is a Cisco thing in here.
All of this started after we installed a Cisco ASA 5500 firewall at our site.
I have one user having email problems. He launches Thunderbird and it checks for messages. After a minute or two, it times out with the server, failing to get any messages. After the first timeout, everything works fine. If you stop it from timing out, it won't work. Outlook Express works fine for him, and Thunderbird works fine for my home computer (and other's).
I've tried uninstalling Thunderbird and reinstalling. Firewall and AVG is off. Note: Outlook Express works perfect, and it's only the first time that Thunderbird times out.
Also, we've tried setting up a VPN client to tunnel to our site, and there is no difference in functionality. Again, for my home computer, it works fine either way.
It seems like the firewall is the issue, but it works everywhere else.
Can there be a timing issue with the firewall? Is there any problem with Thunderbird and a firewall?
(yes, I've tried and am trying the Thunderbird group)