Yesterday Thunderbird stopped receiving or sending emails. When I attempt to send emails, the following comes up: "Login to server outbound.att.net with username manning2887@sbcglobal.net failed." The box also asks for a password; I tried all passwords I thought might be relevant (about 10), but nothing worked. What can I do? I can receive emails at manning120@outlook.com, but of course that email program is not as useful as Thunderbird.