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.

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.

Position your mailbox 41″ to 45″ from the road surface to the bottom of the mailbox or point of mail entry. Place your mailbox 6″ to 8″ back from the curb. If you do not have a raised curb, contact your local postmaster for guidance. Put your house or apartment number on the mailbox.