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Are Mailboxes Waterproof?

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Mailboxes that are compliant with local postal service standards are typically waterproof. However, you may wonder if most mailboxes are waterproof and how to keep out moisture. We researched mailboxes, how to put a stop to wet mail, and other helpful solutions. 

Most mailboxes are waterproof if they follow USPS standards. However, not all mailboxes are constructed watertight and may allow rain, snow, or other forms of moisture to damage mail. Thankfully, many plastic or metal mailboxes are pretty good about keeping water out and mail safe and dry. Do look over your mailbox occasionally to uncover any cracks, holes, or areas that may allow water to get through.

If you are unsure whether your mailbox is waterproof or not, read on to discover more about the structural integrity of mailboxes, as they are essential to safeguarding your mail from the elements.

A black opened mailbox attached to a wooden frame, Are Mailboxes Waterproof?

Mailboxes Fare The Weather

Most mailboxes available for homes or already pre-installed follow regulation standards set by the postal service and are waterproof. You can find a host of spacious, watertight mailboxes made from plastic or metal that keep mail tucked inside safe and dry from all forms of weather.

In some cases, a mailbox may suffer degradation over time and develop cracks, gaps  in seams, or holes, allowing moisture to impact mail. Keep in mind a mailbox may be steel, aluminum, plastic, or wood which will all perform differently over time if located outside.

Two black colored mailboxes

If you notice that your mailbox is always filled with sopping wet mail, it's time to consider replacing your mailbox or patching up any problem areas. You can fill in problem areas and use a couple of coats of waterproof protective spray to seal the exterior. Apply a few coats of waterproof paint to the outside of a mailbox and add a touch of WD-40 to the hinges and joints for easy opening. Galvanized steel mailboxes are one of the best options to have for your mail.

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How Do I Protect My Mailbox From Rain?

If you are worried about your mailbox succumbing to rain and getting mail wet, there are a few things you can do. First off, choose a mailbox that is designed to be watertight.

Seal any cracks or gaps in your mailbox with caulk. Paint your mailbox with waterproof paint and spray on a sealer or wax to resist rain.

Check out this spray sealant on Amazon.

Some other solutions include adding weatherstripping to the mailbox or an overhang to divert rain elsewhere.

How Do You Weatherproof A Mailbox?

A mailbox outside of an American house, How Deep Should A Mailbox Post Be? [A Complete Guide]

Help resist moisture and make your mailbox more weatherproof with a protective sealant. Clean off your mailbox before applying a weather-resistant coat of paint. Apply a generous amount of rubber sealant or boat wax to the exterior of the mailbox.

Inside the mailbox, inspect for any holes, gaps, or areas where moisture can get through and patch them. You can use weatherstripping, caulk, or replace parts of the box as needed to keep rain and snow out. Be advised; you may have to add a new coat of paint and sealant every few years to keep up the protective barrier.

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Do USPS Mailboxes Get Wet Inside?

The construction material and location of a mailbox have an impact on whether it is likely to become wet inside. USPS mailboxes are designed to be completely sealed when shut and locked, keeping unwanted moisture out and mail dry.

It is highly unlikely that a USPS mailbox will become wet inside unless it has been compromised via holes, cracks, or seams. If a mailbox is in humid conditions, it may develop some dampness inside.

Does Rain Get Into Mailboxes?

Mailbox with bills overflowing

Most mailboxes are designed to resist rain and becoming wet inside unless they are tampered with or have significant damage. Rain can enter mailboxes with unsealed cracks, holes, gaps, and if it lacks a non-waterproof coat of paint or a waterproof sealer.

Humidity can cause moisture buildup in mailboxes and potentially develop wet mail. Check your mailbox routinely and fix any damage which can allow rain to damage mail.

Rain can sneak into mailboxes and dampen mail, so consider installing a protective liner for the interior. Make sure the door of the post box isn't loose and closes tightly. Also, consider choosing a mailbox with a recessed door and a rain guard to better protect the mail.

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How Do You Keep Water Out Of Your Mailbox?

Leaking mailboxes are not an unheard phenomenon, as mailboxes that are located outdoors are subject to the whim of the elements for years. Use these tips to keep water at bay:

  • Keep water out of your mailbox by being proactive and coating the inside and exterior with waterproof paint.
  • Regularly clean your mailbox of dirt, grime, and anything that can contribute to the box's degradation.
  • Use sealant strips inside the mailbox where there are gaps or cracks, or use a spray sealant.
  • Apply a premium boat or automobile wax to the exterior of the mailbox to resist rain and moisture.
  • Air out a mailbox if there are longstanding humid conditions and dry out the interior.
  • Ensure the mailbox isn't bent anywhere, compromising the seal, tighten loose screws, and apply caulk as needed.

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How Do I Keep My Mailbox From Rusting?

If you find that your mailbox is riddled with holes and deterioration from rust, it is possible to save your mailbox and avoid replacing it outright. Prevent rust from taking over your mailbox by cleaning the interior and exterior thoroughly with an all-purpose cleaner. Remove any debris and allow it to dry before applying a few coats of a protective sealant. 

If you discover that your mailbox already has visible rust, scrub off any damaged areas. Use a solvent or homemade cleaner with a heavy-duty brush or steel wool. Rinse off the mailbox and allow it to dry fully.

Add some coats of waterproof paint after patching any holes or damage with strips, caulk, etc., as needed. The last step should be to apply a few coats of sealer or wax to keep moisture out. Do realize, that mailboxes left outside will need fresh coats of paint and new applications of weather-resistant wax or sealant over the years.

Check out this protective spray against rust and corrosion on Amazon.

In Closing

A black opened mailbox attached to a wooden frame, Are Mailboxes Waterproof?

We hope that you feel more confident about deciphering whether your mailbox is waterproof or not and how to make a mailbox waterproof. Thankfully, since most mailboxes are made from steel, aluminum, or plastic, these materials are naturally resistant to moisture. However, it is beneficial to routinely replace the coat of paint on the surface of your mailbox, patch or caulk any holes, cracks, gaps, and tighten loose screws and bolts.

The design of a mailbox is to keep the elements out and mail dry when it is closed shut. It is essential to regularly inspect your box for dings, dents, bends, and anything contributing to letting water inside.

In most cases, it is easy to restore a mailbox in the event of rust, holes, or other problems without resorting to replacing the unit altogether. Remember, USPS-compliant mailboxes are designed to be waterproof and last a long time.

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