There is no specific provision for a name. The only thing you can use and which is shown to you by default is the subject line. A possible alternative to templates is the Stationery addon which provides a picker to choose amongst multiple stationery documents, and here you could name them as you wish. Both of the above have the annoying characteristic that they work for new messages but can't be used in replies, and indeed the Stationery add-on solution is problematic in that it destroys what you have already written if you decide to change the stationery in mid flow. Or for yet another approach, look at the QuickText and Clippings addons, which allow you to paste in arbitrary text from a store. I like and use Clippings because it works in both Firefox and Thunderbird so I can share one common set of snippets between both programs. It can be set to prompt you at the point of use for text you type in, such as a name, which will be automatically inserted into the message at the appropriate places.