Message Paper

A sheet of fine paper - usually white but the edges of the cut paper are purple (as if the core of the paper were purple - not like it has a border)

You write on one side of the paper, fold it, and then write the name of the recipient on the outside of the fold (so it is the only thing showing).  Then by snapping it up in the air, it teleports to the recipient.

An interesting story in the Adventurer's Inn tells of how a disguised person was exposed with a sheet of Message Paper.