During the American Civil War, was there mail service between the North and South?

I have heard of communications between the North and South during the Civil War. Other than spies, how did such interactions occur, if there was not mail service?During the American Civil War, was there mail service between the North and South?
Mail connections between the North and South were completly cut. You could get passes to go across the lines, usually women did this with the excuse of sick reletives, and the letters were sewn into hems and sleeves. They weren't technically spies, but they were doing something that wasnt allowed. During the latter part of the Civil War, there was almost no mail service in the south because the North was destroying their rail lines. There is a book about communication during the civil war, but I cant remember the name of it, lot of help I am.During the American Civil War, was there mail service between the North and South?
Lots of travel by merchants and visitors. There were even business transactions. The borders were basically open.During the American Civil War, was there mail service between the North and South?
Samuel Colt got rich with his

special type of pakets sent to both.