Ummm, I believe the answer is "It's not very likely." As in 'Never.'
Enigmail is an extension for Thunderbird and Seamonkey MAIL
. Thunderbird is a standalone mail client. Seamonkey is an 'Internet suite.'
Firefox is a standalone browser.
If you are using Enigmail in Thunderbird, you would use a browser such as Firefox to download the Enigmail XPI (Installation package) to your computer so it may be installed in Thunderbird.
In Seamonkey, the mail and browser components are integrated so you may install directly from the web page.