I sent 5, and received 18 surprises (across LetterMo, InCoWriMo and SendSomething)
Replies to these surprises, I sent 9 replies and received 1.
With existing penpals, I sent 16 letters and received 16 letters.
Other items, 1 package went out, 2 came in. I also received 3 other items of mail from existing contacts, and send a letter to someone new via another hobby.
I sent 66 Postcrossing postcards plus another postcard sent to Portugal for the "boss" and received 23 postcards.