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Best Draught Excluder for a Front Door with a Letterbox: Five Picks That Seal the Gap
A letterbox is the one gap most door seals ignore, and it is often the coldest. This guide covers five ways to close it: brush-and-flap covers, a full replacement letterbox, a magnetic mat, and a bottom-of-door seal to finish the job. It suits renters who want a no-drill fix, homeowners replacing tired hardware, and anyone chasing wind noise as much as cold air. The overview table below sorts the picks by job and price tier so a choice can be made in under a minute.
The Picks at a Glance
| Product | Key Spec | Best Use | Price Tier |
|---|---|---|---|
| STORMGUARD Internal Letter Box Draught Excluder | White PVC, brushes and flap | Budget internal cover | Budget |
| 12 inch (30cm) Door Letterbox | Fits 40–80mm doors, anti-snap flap | Full letterbox replacement | Mid |
| Merriway StormSeal Letter Mail Box Brush Cover | 343 x 80mm, internal or external | Flexible fitting on either side | Budget |
| MAGMAN Magnetic Mailslot Cover | 100mm x 340mm, magnetic seal | Tool-free, removable cover | Mid |
| 36" Door Draft Stopper | Self-adhesive, 36 inch length | Sealing the bottom gap too | Budget |
1. STORMGUARD Internal Letter Box Draught Excluder Cover with Brushes & Flap – White PVC
Type: Internal letter box cover
Material: PVC with brushes and flap
Colour: White
Mounting: Screw-fixed over the existing letterbox
Intended use: Blocking draughts on the inside face of the door
This is the straightforward fix: a white PVC cover that mounts on the inside of the door over the existing letterbox opening. Twin brushes let post through while a flap drops shut behind it, so the gap is closed whenever nothing is passing through. The plastic build keeps the cost down and wipes clean easily. It is the pick for a household that wants the letterbox sealed without replacing the door hardware.
It earns its place as the budget starting point, and it suits renters and DIY-averse buyers who just want the cold stopped. Buyers who want a metal letterbox or a tidier external look should look at the replacement option instead. Trade-off: the PVC cover sits proud of the door’s inner face, so it can catch on coats or bags hung nearby and is not the most discreet look.
2. 12 inch (30cm) Door Letterbox – Fits 40–80mm Doors, Anti-Snap Flap, Internal Draught Excluder
Type: Full replacement letterbox
Size: 12 inch / 30cm
Door thickness: Fits 40–80mm doors
Flap: Anti-snap
Draught control: Internal draught excluder
Finish: White/White
Compatibility: UPVC, composite and wood doors
Where the first pick is a cover, this is the whole letterbox. The anti-snap flap is the headline feature: it resists being forced open from outside, which matters on an external door. An adjustable sleeve spans 40–80mm doors, so it fits most modern UPVC, composite and timber doors without guesswork. The internal draught excluder does the sealing job that a bare letterbox leaves open.
This is the pick for a homeowner whose existing letterbox is loose, broken or simply draughty by design. It also suits anyone upgrading security alongside draught proofing. Buyers in a listed property or with an unusually thick door should check the measurement before ordering. Trade-off: fitting means removing the old letterbox and re-fixing hardware, which is a bigger job than clipping on a cover.
3. Merriway BH05982 StormSeal Letter Mail Box Brush Cover Draught Excluder with Flap
Type: Brush cover with flap
Dimensions: 343 x 80mm (13.1/2 inch x 3.1/8 inch)
Material: Plastic with brush pile
Colour: White
Intended use: Internal or external
Mounting: Fixed over the letterbox opening
The StormSeal is the flexible one: the same cover is rated for internal or external use, so it can go on whichever face of the door is easier to work with. Brush pile lines the opening and a flap closes over it, a combination that blocks draughts while still letting post slide through. At 343 x 80mm it is sized for a standard letterbox plate. The white finish blends with most door colours.
It suits buyers who want a simple cover but need the option of an outside mounting, and it is a sensible pick for a shed or outbuilding door too. Buyers with an oversized or unusually narrow letterbox should measure first. Trade-off: an external mount leaves the plastic exposed to sun and weather, so it will discolour and wear faster than an internal one.
4. MAGMAN Magnetic Mailslot Cover – Satin White, 100mm x 340mm
Type: Magnetic letterbox cover
Seal: Magnetic closure
Dimensions: 100mm x 340mm
Finish: Satin white
Insulation: Thermally insulating
Mounting: Magnetic, no drilling
The MAGMAN takes a different approach: it seals magnetically rather than with brushes or a hinged flap. The result is a cover that lifts away for post and settles back flush, with no screws and nothing to adjust. A thermally insulating layer backs up the seal, and the satin white finish is a step up in looks from plain plastic. At 100mm x 340mm it is sized to sit over a standard letterbox.
It suits renters and anyone who will not drill a door, plus households that want a cover removed easily for cleaning or summer. Buyers who want a permanent, tamper-resistant seal should choose the replacement letterbox instead. Trade-off: a magnetic hold depends on a steel door or a steel letterbox surround, so it is not a universal fit and can be knocked loose.
5. 36" Door Draft Stopper – Self-Adhesive Under-Door Seal
Type: Under-door draught excluder
Length: 36 inch
Mounting: Self-adhesive
Colour: White
Intended use: Bottom of doors
Benefits: Blocks cold, noise and wind
This one does not touch the letterbox at all, and that is the point. Sealing the slot without sealing the bottom gap leaves the door half-done, and this self-adhesive strip closes the gap under the door in one pass. The 36 inch length covers a standard door width, and the adhesive backing means no tools. It also takes the edge off noise and wind whistling under the door.
It suits anyone who has already covered the letterbox and still feels a cold floor draught, and it pairs well with any of the picks above. Buyers with a very uneven threshold or a large gap should check the strip will make contact. Trade-off: adhesive strips can lift over time on a door that is opened and closed constantly, and the strip will need replacing sooner than screw-fixed hardware.
Before You Buy
- Material: PVC and plastic covers are cheap and easy to clean; metal replacement letterboxes last longer and look sharper on a front door.
- Size: Measure the existing letterbox plate before ordering anything, since covers are sized to fit standard openings and a mismatch means a return.
- Compatibility: Magnetic covers need a steel door or surround, while replacement letterboxes state a door-thickness range that must be checked.
- Mounting: Screw-fixed covers seal best but need tools and leave holes; magnetic and adhesive options are tool-free but less permanent.
- Internal or external: An external cover is exposed to weather and will age faster, so an internal mount is preferable where the door allows it.
- The whole door: A letterbox cover does not seal the bottom gap, so budget for an under-door strip as well.
- Care: Brush covers collect dust and lint and need occasional cleaning to keep the seal effective.
Frequently Asked Questions
-
What is the best draught excluder for a front door with a letterbox?
For most homes, a brush-and-flap cover mounted on the inside of the door is the quickest fix, while a full replacement letterbox is the better long-term answer if the existing hardware is worn. -
Do letterbox draught excluders stop all the cold?
They close the largest gap in the door, but the bottom gap also lets cold in, so pairing a letterbox cover with an under-door strip gives the best result. -
Can a letterbox cover be fitted without drilling?
Yes. Magnetic covers and self-adhesive strips need no tools, while brush covers and replacement letterboxes are typically screw-fixed. -
Will a letterbox cover still let post through?
Brush and flap designs are built to let letters pass while closing behind them, and magnetic covers lift for delivery and settle back into place. -
Is an internal or external letterbox cover better?
Internal is generally better where it fits, because the cover is protected from rain and sun and lasts longer. -
Can a draught excluder help with noise as well as cold?
Sealing the gaps reduces wind whistle and outside noise, though it will not soundproof a door on its own.
Bottom Line
For most front doors with a letterbox, the STORMGUARD Internal Letter Box Draught Excluder Cover is the pick that solves the problem fastest: it mounts inside, seals with brushes and a flap, and costs little. Buyers replacing worn hardware should step up to the 12 inch replacement letterbox instead, and anyone still feeling a cold floor should add the under-door strip. Check the current price on Amazon before deciding.
