This is the expected behavior. Learn what the master password does and what not. http://kb.mozillazine.org/Master_password http://kb.mozillazine.org/Protect_the_profiles_contents

Thanks for the response. I'm not sure how this helps. When the email account password is configured in thunderbird, the customer is relying on the master password of the thunderbird client to provide security. If the master password does not do this, what is the point of the thunderbird app? It provides no security into the email account at all as far as I am aware. Is there a way for the thunderbird client to force authentication into the email account?

When the email account password is configured in thunderbird, the customer is relying on the master password of the thunderbird client to provide security.

What do you mean by that? What the master password does is to protect the account passwords Thunderbird has remembered. No more and mo less. For anything else please refer to the article linked above.

Is there a way for the thunderbird client to force authentication into the email account?

You always have to authenticate in order to retrieve new mail. To protect the contents of the profile please refer to the article linked above.