This document describes how to remove the stored password from Thunderbird and enter a new one. Follow these steps if you have recently changed or reset your Office 365 email account password, and you use Thunderbird to save your email account passwords.
Note: These steps will not change the password to your email account, only the password that has been saved in Thunderbird. To change a Office 365 email account password, see the Reset NetID Password section of NetID - Modifying your Account.
Click the Security button, and go to the Passwords tab. Click Saved Passwords....
Click Show Passwords. You may be prompted for the master password.
A box will appear that says Are you sure you wish to show your passwords? Press Yes.
If you have opted to save both your incoming (imap://) and outgoing (smtp://) mail server password in Thunderbird, you will see them listed separately even though they are technically the same password, as shown below. To change a stored password, highlight it and press Remove.
Close all windows and quit Thunderbird.
Thunderbird will attempt to check the incoming server for new mail, at which point it will prompt you for a new password (provided you deleted the incoming server password). Enter the new password and check Use Password Manager to remember this password. Press OK.
If you deleted your outgoing server password, you will be prompted to re-enter your password the first time you try to send a message from your account.