Email passwords and their actions are administered by email providers. Thunderbirds only involvement is to store the password, if you selected that option, and to provide it to the server when asked.

The master password is to protect access to your saved passwords and not to your mail. http://kb.mozillazine.org/Master_password

If someone is accessing your account through the Internet web mail interface, Thunderbird has nothing to do with that.

I understand my email provider admins passwords, but they do not control the functions on the Thunderbird email program. When I access TB, a pop-up asks for a password (the one when I setup my TB email acct) but there is also a cancel button in that same pop-up. All one has to do is hit cancel and they have access to my email.

I guess it helps if you understand how email works. The password request that you see is the email server asking for a password to connect to the server and download new messages. Thunderbird is just relaying that request to you. It has nothing to do with protecting the email already downloaded to you computer. If you are concerned about unauthorized usage use the security built into your operating system to control access to your computer.

Ok Thanks....that is helpful....Couldn't TB add such protection and security?