While I think it certainly is a valid idea, I am going to hold myself to the current no no practice of sending my postcard prints in an envelope.
In my postal system (which is currently not functioning thanks to a labour dispute) that lets me send three 4.7x7 prints at a normal letter rate.
While I know it is a no no to some the fact that I can cram in three postcard sized images, and still pay the same as if mailing just the postcard justuifies it for me. It also lets me send all sorts of images on old paper styles that would otherwise never survive as raw postcards.
Thanks for all that you do in these exchanges.
Anybody heard how Randy, founder of the Postcard exchange, is hold up these days?
Last I heard, perhaps two years ago, he was weighed down with family responsibilities.