exchange mail comes to your @whatever handle, but the money from the sale is deposited directly to the specific toon that posted the item for sale.

So, if you posted a shield for sale on the exchange while logged in to joe@stupidhandle, but the item sold while you were playing bob@stupidhandle, you'd see the sale mail, but if you look at bobs inventory, no new money. You'd have to log back in as joe@stupidhandle and look at his inventory to see the money.

Works the same if joe posts, you log out, come back, log in as bob.

Hope that helps.