**I found the solution to this on http://kb.mozillazine.org/Password_rejected post. Outlook.com, Hotmail, live.com won't work with some programs if the password is longer than 16 characters. My new password was. Change it to a 16 character pwd and mail comes in just fine.** I had to change my outlook.com password yesterday and now Thunderbird will not send mail using that account. I can send via gmail smtp, but not outlook's smtp. I receive just fine, and my imap folders are all updating so Tb is communicating just fine with outlook.com, but it will not send. I get Login Failed error message and am asked to reenter the password repeatedly. I am able to write the messages in Tb, save them as drafts and then go online in outlook.com and send the draft from there. But Tb will not send directly from the program. I am able to send with my iPad and iPhone through the mail app using my outlook.com account. I have been using Thunderbird for years and have not changed the smtp settings. I have tried deleting and configuring the smtp settings. I have changed the outlook.com password a second time as well. None of this has helped. I tried turning off my firewall and disabling the antivirus. No luck. The error started yesterday, today Tb updated and the error has continued. I am considering a fresh install of Tb, but don't have much hope that will help since the error has persisted even after the update this morning. I'm running Tb 38.3.0 Windows 7 pro, SP1, 64 bit