Architectural Mailboxes - Basic In-ground Post Black - Post haste. If you need a mailbox post put in the ground quickly and easily, this is the one for you. This simple, in-ground post is crafted of galvanized steel and powder coated to compliment your mailbox. With mounting hardware and instructions included, you&rsquo;ll be able to have it up in no time.Constructed of galvanized steel and powder coated to match your mailbox. Finish is fully powder coated  Includes all mounting hardware and instructions post is 2mm galvanized steel Support plate is 1.2mm galvanized steel Works with 5500 series and 6200 series