Since 2008, the Mail Art Postcard Exhibition has been accepting and displaying mail art cards on their blog. The pieces are mostly presented without comment and there is something both soothing an inspiring about scrolling though those years of art. There are occasional themes you can participate in if so inclined. The simple intro at the top reads, "This is a curated exhibit of mail art postcards. All media are welcome. Not all cards submitted will be posted. Artists may send their pieces by postal mail to this address:
P.S. I found this link from this article by another mail artist named Brent Leopold "The Human Artist Vending Machine" which was sent to us by member Christina. Thanks Christina!