A few years ago I began painting and mailing postcards to myself when I traveled overseas. It's so much fun to come home from a trip, and a few days later, receive a reminder of a particular moment. Plus, it's fun to have a collection of foreign stamps. The card above is one that I painted while in France.
Before leaving home, I cut a few "postcard" size pieces (4.5" x 6.5") of Arches 300lb paper. I always go to an overseas post office to verify mail cost and I've never had a problem mailing them. They've always arrived home none-the-worse-for-wear, even though I don't seal the paper in any way. I suppose if the mailman delivers them in a pouring rain though, there might be a problem.
In October I'm traveling to Italy and am thinking of offering to paint and mail a postcard to folks that pre-purchase.
The price would be $30 per card (a real deal for an original piece of art!) If you're interested, send me an email!