Where did the phrase "you read my mail" originate?

Question

Who has heard of this? Is this an American or Canadian phrase, or all over the world? "You were reading my mail" as in you understand what I'm saying.

Answer 1

I have heard the idiom used and in the manner that you mention ("You read my mail" to mean "You understand"). I do not know the origin, but this use of the phrase is relatively new. It does seem to be located only in North America, but the way communication travels today, it might have spread.