I was a bit dubious on this one until I tried it. Its a bit goofy but could be very useful. It gives you a drop-down in the search box in which you can type a recipients address, then opens your Gmail account with a message ready to type into and send to that address. It could save a lot of time if you work on line refrequently.
I cannot understand what this add-on is supposed to do. No offense, but the English is half-coherent, such that I can't discern whether this add-on is for Thunderbird or for Firefox, much less what it does.