I have already sent out a few of them. One of my favorites is this one to Katerina in Greece - Greek airmail envelopes used to have blue edges, but lately she has been unable to find them - aargh, the slow death of snail mail.
Update!! The same week that Katerina received my 'Greek airmail' envelope, she found a stash of envelopes in a small shop - so she'll be sending them out again.
I also sent moons to Eduardo Munez, Bridget and Eva.