No one here has anything to do with your email password. Email passwords are administered with your email provider. Contact them for your options to reset your password. Most providers have a reset option on their email help page. If you have told Thunderbird to remember your password you can see what was saved and edit what is there by going to ... Options-Security-Passwords-Saved Passwords Click Show Passwords Right click the password and select edit.

You still have to change the password at your provider. The above only modifies what is saved in Thunderbird. Log into your account at the providers webmail page and make sure you have a working username and password there before messing with Thunderbird.