When you start up computer you should get asked for a password to your computer User Account. That is the first level of security and it's important. No one can access your User Account to see your desktop or personal documents unless they also have access to your computer User Account and that also includes Thunderbird. So you already have a first level of protection for Thunderbird. If you start Thunderbird and want to see saved passwords then you will get asked to input that User Account password. It means should anyone be present and looking over your shoulder at that moment in time you can cancel and prevent anyone seeing stored passwords. Some people also choose to set a 'Primary Password' which only protects access to viewing saved passwords in Thunderbird. That 'Primary Password' is useful if you share your computer AND your computer User Account password with other people. If you do not share computer with other people and do not share your User Account password with other people AND you never leave your computer running and logged on to User Account when you are not present then the Primary Password is somewhat surplus to requirements. It's only blocking your own viewing. Other programs on computer do not generally ask for a password in order to run the program itself eg: Microsoft Office suite or OpenOffice or Paint etc. Passwords are only asked when logging on to something like a User Account on computer or a program that is directly accessing a server. Thunderbird does not need a password to run the program. It does need passwords to access saved passwords and it does need mail account passwords to access servers. Many servers do use OAuth2 or require 2FA, but that is specific to that server.