KeeBird is an extension for the Thunderbird email client that communicates with the KeePass Password Safe to fill in authentication information.
KeeBird is a fork of KeeFox 1.8. In the past, it was possible for the same extension to work with both Firefox and Thunderbird, however with the shift to web extensions in Firefox 57, it is no longer possible for the same extension to work for both. Now, Kee 2.x is the extension for Firefox and KeeBird is the extension for Thunderbird.