The Download Now link will prompt a local download of the Thunderbird extension. To install the extension directly, open Add-ons from the Tools menu. From the options button next to the add-on search field, select "Install Add-on From File..." and locate the downloaded add-on.
Muttator is a free browser add-on for Thunderbird, which makes it look and behave like the Vim text editor. It has similar key bindings, and you could call it a modal mail client, as key bindings differ according to which mode you are in.
Full Specifications
What's new in version 1.1
General
ReleaseAugust 27, 2012
Date AddedAugust 27, 2012
Version1.1
Operating Systems
Operating SystemsWindows, Windows XP, Windows Vista, Windows 7