Large Mailbox for Packages: Sizes, Locks and Install Tips

A standard mailbox was designed for letters, not for the boxes that show up several times a week. When parcels do not fit, they end up on the porch, in the rain or in the hands of a passing thief. A large mailbox for packages fixes that by giving carriers a secure place to leave most deliveries, often behind a locking door or an anti-theft drop chute.

Choosing one comes down to four decisions: how big your typical parcels are, if you want a simple oversized box or a locking parcel unit, where the box will mount and how strong the post or anchors must be. Bigger, heavier boxes need sturdier posts and deeper footings, and if you dig, call 811 first so buried utilities get marked.

Choosing a Large Mailbox for Packages

Start with the parcels you actually receive. Look at the last month of deliveries and note the common box sizes. Many online orders arrive in small and medium boxes or padded mailers, which an extra large mailbox can swallow easily. Large appliance parts, bulk household goods and oversized boxes may never fit, so plan for a backup spot for those.

Main types

• Extra large curbside mailbox: a big version of the familiar arched box. It holds bigger mail and small parcels but usually has no lock.
• Extra large rural mailbox: a deeper, taller box common on rural routes, sized to handle more mail and small packages between pickups.
• Locking parcel mailbox: a tall cabinet-style unit with a drop door or chute for the carrier and a locked retrieval door for you.
• Wall-mounted parcel box: mounts near the front door, good where carriers deliver to the house rather than the curb.
• Freestanding parcel drop box: a stand-alone unit bolted to a porch or pad, sized for frequent large deliveries.

Size and Capacity

Capacity is listed differently by different sellers. Some give interior dimensions, others list the largest box that fits through the opening. The opening matters more than the interior, since a carrier cannot drop a parcel that does not fit through the door or chute.

• Opening size: measure the slot or door, not just the cabinet. A deep cabinet with a narrow slot still rejects mid-size boxes.
• Interior height: tall units hold stacked parcels from multiple deliveries in a day.
• Weight capacity: the floor and hinges should handle heavier items such as bottled goods or small hardware orders.
• Mail separation: some units have a separate letter slot so flat mail does not get buried under parcels.

For a large mail box at the curb, a common sweet spot is a unit that fits a medium shipping box through the door. Households with multiple daily deliveries often step up to a tall locking cabinet.

Anti-Theft and Locking Features

Security is the main reason many people upgrade. The best parcel mailboxes use a one-way drop that lets the carrier put packages in but stops anyone from reaching back out.

• Rotating drum or chute: the parcel tips into the locked cabinet when the door closes, and the chute blocks reach-in access.
• Locking retrieval door: key or combination lock on the main compartment. Keyed locks with two or more keys are standard.
• Heavy-gauge steel: galvanized or powder-coated steel resists prying better than thin sheet metal or plastic.
• Concealed hinges and bolts: mounting bolts accessible only from inside the locked compartment stop thieves from unbolting the whole box.
• Weather sealing: gaskets and drip edges keep cardboard dry in storms.

Note that some carriers will not leave mail in a box that requires a key to deposit. Locking units designed for delivery leave the deposit side open and lock only the retrieval side.

Placement and Postal Guidelines

Curbside mailboxes must meet postal placement standards so carriers can reach them from a vehicle. General guidance in most areas places the bottom of the box (or the point of mail entry) at roughly 41 to 45 inches above the road surface and the front of the box about 6 to 8 inches back from the curb or road edge. Parcel lockers and taller units may have different requirements. Always confirm with your local post office before installing, because rules and route conditions vary.

• Place the box on the right side of the road in the direction of travel for the delivery route, unless your local carrier says otherwise.
• Keep the approach clear of parked cars, trash bins and snowbanks.
• Add your house number to the box, ideally on both sides, in contrasting digits.
• For wall-mounted parcel boxes, mount near the entry where the carrier already walks.
• Check HOA rules, which may limit style, color or size.

Posts, Anchors and Footings

A tall extra large mailbox for packages is heavier and catches more wind than a standard box, and a full one is heavier still. A post that held a small mailbox may not be enough.

• Post choice: a 4×4 treated wood post works for many large curbside boxes; heavy steel parcel units often call for a steel post or a manufacturer-designed pedestal.
• Depth: typical posts go about 24 inches deep; in cold climates go below the frost line to prevent heaving.
• Concrete: set heavy units in concrete for stability. A wider footing resists tipping under load and wind.
• Breakaway consideration: some areas encourage or require posts that yield if struck by a vehicle. Massive brick or heavy pipe posts near the road can be a hazard; check local guidance.
• Pad mounting: freestanding parcel boxes bolt to a concrete pad or porch slab with masonry anchors.

An extra large mailbox with post sold as a combo kit simplifies matching the box to the support. Check that the kit’s post is rated for the box’s weight.

Tools and Materials

• Mailbox or parcel unit with mounting hardware
• Post (wood, steel or kit pedestal) and mounting plate
• Post hole digger or auger, shovel and tamping bar
• Gravel and bagged concrete mix
• Level, tape measure and drill/driver
• Masonry bit and anchors for pad or wall mounting
• Gloves and safety glasses

How to Install a Large Parcel Mailbox on a Post

1. Confirm placement. Check height and setback guidance with your local post office and any HOA rules.
2. Call 811. Request utility marking a few business days before digging. Lines often run along the road edge.
3. Dig the hole. Make it at least 24 inches deep and roughly three times the post width; go deeper below the frost line in cold regions.
4. Add gravel. Pour and tamp 4 to 6 inches at the bottom for drainage.
5. Set the post. Position it so the finished box lands at the right height and setback. Plumb it on two sides and brace it.
6. Pour concrete. Fill around the post, slope the top away from the post and let it cure per the package.
7. Mount the box. Attach the mounting plate, then secure the box with the supplied hardware, ideally bolted from inside the locked compartment.
8. Test the doors. Drop a test box through the chute, lock and unlock the retrieval door and check that rain drains away.

Large parcel cabinets can be heavy. Lift with a helper and set the unit on the plate before fastening.

Typical Costs

As general ranges, an oversized curbside box without a lock is the most affordable option. Locking parcel mailboxes cost noticeably more, and heavy-gauge freestanding drop boxes sit at the top of the range. Professional installation adds labor for digging, concrete and mounting, which varies by region and soil conditions.

Troubleshooting Common Problems

Carrier leaves packages on the porch anyway: the parcel may not fit the opening, or the carrier may not know the box exists. A short note on the box and a word with your local post office often helps.

Water inside the cabinet: check gaskets and drip edges, add a small drain hole at the lowest point if the maker allows, and keep the box level.

Drop door sticks: clean the hinge and drum, and lubricate with a dry lubricant that will not attract dust.

Post leaning: the footing was too shallow or the post too light for the box. Reset deeper in concrete or upgrade to a steel post.

Lost key: many units take replacement lock cylinders; order one that fits the model.

When to Call a Professional

Bolting a parcel box to a porch is a manageable DIY job. Consider hiring a pro if utilities are marked near your preferred spot, if the box is very heavy, if you want a masonry column or if your soil is rocky or full of roots. A local handyman or fence installer can set a post and footing quickly with the right equipment.