When you take your mail to post office to be mailed by 500 pm does it go out that same night?

Whether your mail goes out the same night depends on the post office's processing schedule and cut-off times. If you drop off your mail by 5 PM and the post office has a scheduled mail dispatch for that evening, it should go out the same night. However, if they have already completed their dispatch for the day, it will be sent out the next day. It's best to check with your local post office for specific details.