I wrote a postcard to the NSA making them aware of the fact that they should stop reading my emails while I am in the US.
I typed the postcard on my Triumph-Adler typewriter, because I loved the story about the Russian Intelligence Services going back to typewriters.
In case they can’t identify me by name or by the typeface of the typewriter, i actually licked the stamp (mormally I use self-adhesive stamps).
Oh, and, dear NSA: You’re probably reading this. So: I’m always happy about mail art. Feel free to send me a reply to my P.O. Box. You know where to find me.