Mailing a banana is something I was wondering about when I first saw this thread. I remember seeing a photo in a book many years ago of a banana with a postage stamp on it and I was wondering whether it was really possible.
Did the book make it to Magrathea?
As one of the wealthiest planets in the galaxy, I'm sure it did because of Magrathea's exceptional central planning infrastructure.
We successfully mailed two bananas in college. The second was to ensure that it actually left campus and round tripped via USPS.