Google maps directed me to City Hall/Hotel de ville, which was scary because there are armed guards at the front. If you enter the square with the column thing in the middle, the city hall is one side of the square, and the post office is the side to the right. You can also look up at the carvings and find the post office because it has lions (or ask a guard).
I just needed to post some postcards, and the stamp machine had an English language option, so I can't speak to the rest of the post office services. read more