I have a Verizon.net email account. It was migrated to AOL servers several years ago. I migrated successfully at that time. Suddenly, two days ago, I began getting error message when trying to send outgoing mail from my Verizon.net account in Thunderbird. Error message says: "Login to server smtp.verizon.net with username xxxxx failed." I can still send email from the Verizon.net address from my mobile device app, so it looks like a Thunderbird problem. I have the current version of Thunderbird installed. None of the Thunderbird account settings were changed or corrupted from what they have been for years. I'm using a PC. The same thing happened to my wife who uses a Mac.