No,they don't.
You Trade a Pokemon holding a piece of MAIL.
You can write letters to your friends. Just put a message on the mail. Give the mail to one of your pokemon, and trade with a friend.
there is no way you can trade mail on pokemon black
go to slateport and by 1 habor mail then go to the lady's house next to the game center and trade it with her.
You can buy Harbor mail at Slateport City
Nothing,its just a different design of mail
I'm no expert, but I think you mean people in the game. I know for sure how to trade skitty for Meowth go to Battle Frontier and go left past Battle Tower, go into the room and do the trade. Meowth will be holding Retro Mail if you are lucky.
Give it a mail item and trade it.
Unduplicatable ItemsThe only Items you can't duplicate in Emerald are Mails, because you can't store a Pokemon holding Mail into a PC. You can't clone any Key Items either.
Trade it
go to slateport store and buy a harbour mail then go up to mauville city and go in to the house right of the casino and trade the mail for a coin case to the lady
Harbor mail