BT mail premium mail
I can receive but can't send BT Premium Mail through Thunderbird
Todas as respostas (2)
See https://support.mozilla.org/en-US/questions/1295861 for a possible solution.
Or, in short terms try to set security.tls.version.enable-deprecated to true From the menu at the top right, go to Options. Scroll all the way to the bottom and click on Config Editor. Skip past the warning. Scroll down until you find security.tls.version.enable-deprecated (or paste security.tls.version.enable-deprecated to upper frame)