I have used Thunderbird for years with my company's Google Mail account. This morning, I can't send any messages in Thunderbird (incoming still works fine). When I try to send, I get the message "Login to account Google Mail failed" and asking me to enter my password. I do - and it's correct, I verified using the online Gmail interface - but the window just pops up again and again. When I finally hit cancel, the attached pops up. Again, the login is correct, and I have not changed any of my outgoing mail settings. They've worked for years. And incoming messages continue to work fine. I can send email no problem via the Gmail interface. I'm on a Mac with the latest version of Thunderbird. The problem began with an older version (48 I think). I updated to the latest this morning and it didn't fix anything.