As someone that has not received a "weird" mail, I'm now going to be more cautious based on what I've seen on this thread...
A letter that was supposed to be sent to Taiwan, but ended up in Europe .. my mailbox. No similarities in the name or address. Forwarded it to the specified recipient afterwards.
Money was a weird one for me. Only because besides in bday cards I always for some reason thought you shouldn't do it, but I had a visa agency once send me my change in coins in the mail internationally haha. Was so strange to me.