Thunderbird won't connect to server.

I've used Firefox and Thunderbird since their inception, and Netscape before that. I am Not a 'newbie' user. Recently, Thunderbird stopped connecting to my server. The app lights up green as it searches for the server for a minute or so then stops after not connecting. I've tried re-configuring the server connections in 'tools' to the recommended settings on the Mozilla site. I've made sure my firewall isn't blocking the app. I've used Revo-Uninstall to completely uninstall the app and re-installed after system re-start - several times. I've tried running it with add-ons disabled. Nothing works. Thunderbird still won't connect to my mail-server. I use Comcast internet and mail and that is the only email I have configured for Thunderbird. My email through Comcast online works fine. Please help! _{edit: removed your mail address from public display, since the only thing it will attract are spam bots. you will be notified per mail once somebody replies to the thread. (philipp)}