This morning my husband opened Thunderbird, downloaded his emails and attempted to reply to one and received first the Sending message box, jpg1, then almost immediately login failed jpg2. when he tried to send again the Send button was greyed out, jpg3 I attempted to resolve the issue, with a new password, changing settings, all with no success. As I also have Thunderbird on my computer I checked and got exactly the same problems, and nothing has changed on my computer since I sent six emails yesterday. Both computers have identical SMTP settings, apart from the specific email address, and I cannot believe that we have both managed to screw up setting which were perfectly functional on Feb 21st, but now no longer work on Feb 22nd 2019.