You’ve invested in quality locks, secured your windows, maybe installed an alarm. But every day, mail gets pushed through a hole in your front door.
That letterbox is a security vulnerability most people never consider—until something goes missing. It’s a critical component of your overall front door security.
How Letterboxes Become Security Risks
Letterbox Fishing
The most common exploit:
- Criminal opens letterbox flap
- Inserts a hooked tool (wire, stick, fishing rod-like device)
- “Fishes” for keys left on tables, hooks, or nearby surfaces
- Retrieves keys and walks in through the front door
What Else Gets Stolen
Through letterboxes, criminals take:
- Keys (as described)
- Wallets and bags left in hallways
- Hanging coats with items in pockets
- Delivered packages sitting on the floor
- Car keys (particularly valuable)
Lock Manipulation
Sophisticated attacks through letterboxes include:
- Reaching internal door handles
- Manipulating lock mechanisms
- Using tools to turn thumbturn locks
- Inserting borescopes to survey lock types
"The letterbox is designed for mail to enter. Unfortunately, it’s equally effective for tools to enter—and your belongings to exit.
The Reach Zone
What’s Within Arm’s Length?
Stand outside your front door. Open the letterbox (or have someone else do so). What can they reach?
Typically:
- 30-50cm interior depth with arm only
- 100cm+ with hooked tools
- Floor level to hand-height range
Common Danger Zones
Key hooks near the door: The classic mistake. Keys hanging on the wall “for convenience” are fishing targets.
Hall tables: Keys, wallets, phones left on hall furniture are reachable.
Low shelves or coat pockets: Anything at floor to waist height on hanging coats.
Door handle (internal): If your internal lock has a thumbturn or lever accessible from the letterbox angle, it can be manipulated.
Letterbox Security Measures
Letterbox Cages (Interior Guards)
A metal or wire cage fitted inside the door:
- Catches mail safely
- Prevents tools reaching through
- Blocks hand entry
- Doesn’t stop mail delivery
Letterbox Restrictors
Metal plates or mechanisms limiting opening angle:
- Letterbox opens only partway
- Mail enters but hands/tools don’t fit
- Can be retrofitted to existing letterboxes
- Various designs available
Cowl Letterboxes
Designs where the letterbox:
- Opens downward only
- Interior cowl blocks upward reach
- Mail drops but fishing up is prevented
- Often combined with brush seals
Draught Excluder Brushes
Not security-specific but helpful:
- Stiff brushes inside the letterbox
- Block view into the property
- Make tool insertion more difficult
- Also reduce drafts
Sealed Letterboxes (External Postboxes)
For maximum security:
- Remove letterbox entirely
- Install external mailbox on wall or post
- No hole through the door at all
This is dramatic but eliminates the vulnerability completely. Particularly worth considering if you’re preparing your home for holiday.
Situational Awareness
Key Habits
Never:
- Hang keys within 2 metres of the door
- Leave keys on hall tables
- Keep car keys near the front door (relay theft risk too)
- Place key hooks visible from letterbox view
Always:
- Store keys well away from front door
- Keep spare keys with trusted people, not hidden nearby
- Consider a key safe if you need external storage
Valuables and Bags
- Don’t leave bags on hall floor
- Move coats with valuables away from reach
- Deliveries should be moved promptly
What They Can See
Through the letterbox, criminals also survey:
- Your lock type (planning future attacks)
- Alarm keypads and whether alarm is set
- Movement patterns
- Valuables visible in hallway
Blocking sightlines (draught brushes, internal covers when home) reduces intelligence gathering. Include this as part of your nightly security routine.
Special Considerations
Flats and Maisonettes
- Communal access may already compromise outer security
- Letterbox security becomes more important
- Consider whether you control the exterior
- Cage installations remain possible
Rental Properties
- Discuss installations with landlord
- Non-destructive options available
- Document any attempts for security reasons
- Consider renter’s insurance implications
Listed Buildings
- Some exterior letterbox designs may need approval
- Interior cages typically unrestricted
- Consult if considering external mailbox installation
Installation Options
DIY Installation
Most letterbox cages are DIY-friendly:
- Typically screw-mounted to door interior
- Tools needed: drill, screwdriver
- Time: 15-30 minutes
Letterbox restrictors:
- Often adjustable to existing letterbox
- May require drilling
- Instructions provided with product
Professional Installation
Consider professionals if:
- Modifying door structure
- Installing external mailbox
- Uncertain about correct fitting
- Listed building considerations
Cost-Effectiveness
| Solution | Typical Cost | Protection Level |
|---|---|---|
| Relocating keys (free) | £0 | Essential baseline |
| Letterbox cage | £15-40 | High |
| Draught brush seal | £5-15 | Low-Medium |
| Letterbox restrictor | £10-25 | Medium |
| Cowl letterbox replacement | £30-80 | Medium-High |
| External mailbox | £50-150 | Maximum |
The lowest cost measures provide significant protection. A £25 cage may prevent a £3,000+ burglary.
Frequently Asked Questions
Can burglars really reach through a letterbox?
Yes. With specialized tools, criminals can fish for keys, reach door handles, and even unlock some doors through the letterbox. If your internal lock is within arm's reach, it's a vulnerability.
What is a letterbox guard?
A letterbox guard is a metal cage that fits behind your letterbox on the inside of the door. It catches mail while preventing hands or tools from reaching through to your hallway.
How much does letterbox security cost?
Letterbox guards cost £20-50. Letterbox restrictors are £10-20. Anti-fishing brushes are £5-15. Complete protection is achievable for under £50.
Should I seal my letterbox completely?
Only if you have an alternative mail delivery solution (external mailbox, parcel box). A completely sealed letterbox is the most secure but requires mail to be collected elsewhere.
Can postmen use a restricted letterbox?
Yes. Letterbox restrictors allow mail through but prevent tools and hands. Normal mail delivery is unaffected.
Will my insurance require letterbox security?
Policies don't typically specify letterbox security. However, if a "no forced entry" burglary occurs via letterbox fishing, claims may be complicated.
Are letterbox cages unsightly?
Modern designs are discrete. Some are quite attractive. They also contain your mail neatly rather than having it scattered on the floor.
What is letterbox fishing?
Letterbox fishing is when criminals insert a hooked tool through your letterbox to "fish" for keys, wallets, or bags left near the door. There's no forced entry, making insurance claims complicated.
Take Action Today
Walk to your front door right now.
- Open the letterbox from outside
- Note what you can see and reach
- Identify keys, valuables, or the lock mechanism in range
- Order a cage or make changes immediately
The few pounds and minutes this costs prevents the day you come home to find your keys—and worse—missing.