The Couche Tard post office is open on some holidays that the main post offices are closed. On most weekdays there's a guy there who's very friendly and polite.
Worst costumer service that I’ve seen among Canada posts in Montreal! It’s been 25 minutes that me and another costumer are watching this lady organizing envelops but not doing our work. She does not seems to hurry (while we are all waiting) and does not prioritize customers over other works.