The USPS does not legislate the relocation of residential mailboxes nationally. Rather, they allow local postmasters to decide what is best for their geographic location and mail service. ... It can save you a lot of headache if you take the time to call or visit the post office before moving your house mailbox.

Most mailbox post installations require a 60 lb. bag of dry concrete. Pour a little more water on top of the concrete mix. The concrete mix in the ground will soak in both the water you poured earlier as well as the water from the top.

Measure the height of the mailbox above the ground to ensure it's around 42 inches. Do not bury your post deeper than 24 inches.