encrypt mailboxes?

I telecommute and use a number of desktops and laptops. I've really enjoyed having my email with me via a USB drive. I worry though, what could happen if I ever lost the drive - most likely someone would just wipe it clean for their own use, but what if they did go through my mail?

From searching around through the forums, it appears that there are some ways of encrypting drives, most of which require administrative rights, though some more complex methods may avoid this (?). But it is really just my email that I'm concerned about.

The Thunderbird Master Password appears to block access to stored passwords, but not stored email. So unless I've just missed something, I guess I'm making a feature request. I'd like to see the email storage files encrypted, using the Master Password or an additional password. Maybe this should be posted at mozilla.org?

Or is there already some simple way to do what I want?

Thanks!