Open Thunderbird and go EDIT ACCOUNT SETTINGS SERVER SETTINGS
Check the details in the SERVER box - I dont know your e- mail address - Dont post it here - but it is the bit after the @ synbol that we need - For bt this is @btconnect.com so in the box goes pop.btconnect.com. ( some isps use mail.instead)
In the USER NAME box try your complete e-mail address
CONNECTION SECURITY ssl/tsl
CONNECTION SECURITY Normal password
Click on OK and see what we get.