This is difficult, Thunderbird has a master password that can be set, but it only protects the password store in Thunderbird. Simply hitting the escape key will bypass that. All other account passwords for individual mail accounts will not be available if the master password is invoked and bypassed, but all locally stored mail will be present. As for account passwords for email accounts. Without the master password, you will been to approach the individual mail account providers. There is no way to access the passwords stored in the store without a master password if it is set. Only a method to clear the stored passwords and remove the master password. See https://support.mozilla.org/en-US/kb/protect-your-thunderbird-passwords-master-password