We need to replace our mailbox by the curb. How deep do we dig and how much cement do we pour in the hole. Thanks!
Dig below the frost line in your area. Use a pressure treated post. Pour gravel under the post to aid drainage. Then use one standard bag of cement, and top with gravel. Stamp down well as you finish.
This tutorial might help: https://www.youtube.com/watch?v=8t5MnOOqCf8
Try sika. It is a polyurethane foam that swells to fill post hole. It’s about $10 at Lowe’s.