Start a command terminal and enter "ping steve-lexie.net" to see if you have internet connectivity to the site. (You may have to do a Control-C to stop the pings.) If you get ping responses, then see https://support.mozilla.org/en-US/kb/cannot-receive-messages for further info. If you still have problems, tell us your operating system (Win, MAC, Linux), your version of Thunderbird, and whether you use IMAP or POP.