I asked the town post office if they could put a Christmas card in my grandmas box. Knew I wouldn't run into her and the box was right there in the post office so no sense in mailing it. He did, but made me pay for a stamp, lol.
My deliveryman never complains when I put a card and 20$ in my mailbox for him each year (except the year he was on vacation and the backup rural carrier took it) and I don't have to pay for a stamp