A leaning mailbox post can result from loose soil, frost movement, vehicle contact, or rot at ground level. Resetting it lasts only when the post and the mailbox support are sound enough to hold their alignment through weather and repeated door use.
Inspect before digging
Check the post below the soil line if possible, the mailbox arm, fasteners, and the surrounding ground. Look for splitting, carpenter-ant damage, or rot. Confirm local mailbox height and setback requirements before changing the location.
Remove the load carefully
Take the mailbox off the post and set the hardware aside. Mark the original position and identify utility lines before digging. If the post is broken or badly deteriorated, replace it rather than packing soil around a weak section.
Prepare a stable base
Dig the hole to the required depth for the post and local conditions. Keep the bottom firm and use appropriate drainage material when recommended. Set the post plumb in both directions, then brace it temporarily so alignment does not shift while backfilling.
Backfill and refit
Use suitable soil or post-setting material according to the installation method. Compact in layers and keep the post vertical after each layer. Reattach the mailbox with exterior-rated hardware, check that the door opens freely, and confirm that the box is not facing traffic hazards.
Seal exposed wood ends and inspect after heavy rain or frost. If a vehicle has struck the support, examine the surrounding ground and hardware for hidden damage before returning the mailbox to service.