Try logging into Outlook.com webmail to make sure that your password is correct. Do you have 2-step verification turned on, and use an App Password for use with Thunderbird? If not, then you should do this. [https://support.microsoft.com/en-ca/help/12408/microsoft-account-about-two-step-verification Enable 2-step verification], then you create an App Password to use in Thunderbird. Once you have set an App password for use with Thunderbird, copy that password and paste it somewhere temporarily (like a text file or Word file), for safe-keeping. Then you need to tell Thunderbird to forget the password it has saved for that e-mail account, so Thunderbird will ask for the new password. Thunderbird menu: Tools: Options: Security: Passwords tab Click on the "Saved Passwords" button. If you have only the one e-mail address set up in Thunderbird, then click the "Remove All" button at the bottom left. If you have more than one e-mail address/account setup in Thunderbird, then you need to just remove the "imap" or "mailbox" and the "smtp" lines for that particular e-mail address. Then click the "Close" button, and then the "OK" button on the Options window. Now when you tell Thunderbird to check your e-mail, it will ask you for the password. Paste in the App password you set. It will also ask you for the password the first time you send an e-mail.

Thank you Bruce, everything working ok now.