I need to send mail to a friend who's traveling in Morocco. How much postage do I need for a letter? Can I drop it in any letter box in New York, or does it need any special treatment from the Post Office?
(I hope this question is on-topic for this site. Apologies if it ain't. It seems sort of like a no-brainer let-me-google-that-for-you question, but I've checked the Googles and I haven't found any information that seems likely to be correct.)