One of the quirkiest properties of Thunderbird Mailis that it is impossible to check what password you used for your mail account.
Once used, there is no possibility to check it. and that is clumsy.
My email provider takes the same approach today. If I choose an email password and forget it, I can only request a new password.
Handy, Euh NOT! After that all my devices need than a new password. I love to see that changed.