You cannot reset your email account's password via Thunderbird. You need to go to your '''email service provider's website or webmail portal '''and use the ''forgot password'' link provided there. After you've reset your password, you can then update the copy that Thunderbird saves in its password vault as explained here [[Password Manager - Remember, delete and change passwords in Thunderbird]]. Thunderbird has no control over your email account password. It only stores a copy of it for signing in to your email account when sending/receiving mail.