letterbox friendly boxes

letterbox friendly boxes are slim postal boxes made to pass through a standard letterbox and to travel at Royal Mail large letter rates where the size and weight allow. Custom Postal Boxes, a project of Vertex Packaging based in Wolverhampton, makes letterbox friendly boxes to measured sizes with custom print, low minimum order quantities, free design support and free UK delivery.

How letterbox friendly boxes keep deliveries simple

A parcel that fits through the letterbox does not need anyone at home, a neighbour, a safe place note or a second delivery attempt. That convenience is the whole point of this format. Customers order small, flat products expecting them to simply arrive, and a slim rigid box delivers that experience while protecting the contents far better than a padded envelope.

The format suits jewellery, accessories, cosmetics, stationery, prints, slim books and flat gift sets. Our letterbox postal boxes are built around these uses, and the large letter postal boxes range focuses on the Royal Mail large letter footprint in particular.

The Royal Mail large letter limits that set the size

Royal Mail large letter post allows a maximum length of 35.3cm, a maximum width of 25cm and a maximum thickness of 2.5cm, with a weight limit of 750g for most services. Every millimetre of thickness matters, because a box that bulges past 2.5cm once it is filled moves into small parcel pricing. Check the current service details on the Royal Mail tracked services page before you finalise a size.

Measuring the packed box, not the empty box

Measure the box as it will travel, filled, sealed and labelled. Tissue, a thick card or a product that springs back against the lid can all add thickness. Leave a small margin below the 2.5cm limit rather than designing exactly on it, and weigh the complete parcel so the total stays inside the weight limit as well.

Protection inside a slim box

Slim does not have to mean fragile. Corrugated and solid board in this format resist bending and crushing from the sides, and a close fit stops the contents sliding. For flat items such as prints, a board backed box prevents corner damage that envelopes allow. Sizes based on familiar paper footprints help too, and our A5 postal boxes and C4 postal boxes cover the two most common document and print sizes.

Print on a box everyone sees

A letterbox box lands face up on the doormat, which makes its top panel valuable space. A logo, a colour and a short line of text turn an anonymous delivery into a branded one, and print inside the lid greets the customer on opening. Keep the label area plain so the address and barcode stay clear and easy to scan.

Choosing your letterbox box size

Start with the product footprint, add the protection it needs, then check the total against the large letter limits. Share those figures and the quantity you need when you request a quote. Pricing depends on size, material and quantity, and a made to measure box often removes the padding and oversizing that push a parcel over the thickness limit.

FAQs about letterbox friendly boxes

What is the largest size for Royal Mail large letter post?

The maximum large letter size is 35.3cm long, 25cm wide and 2.5cm thick, with a weight limit of 750g for most services. The packed box, including its contents and sealing, must stay inside all four limits to travel at large letter rates.

Will a large letter box fit through every letterbox?

Most standard letterboxes accept a box within the large letter limits, but letterbox apertures do vary, especially on older doors. The Royal Mail limits are the reliable guide for postability, and keeping a small margin under the maximum thickness helps in practice.

What products fit well in a slim letterbox box?

Jewellery, phone accessories, cosmetics, seeds, stationery, prints, slim books and flat gift sets all fit well. The product needs to sit within the thickness limit once any wrapping is added, so measure the item exactly as it will be packed.

What happens if my packed box is thicker than 2.5cm?

It will be priced as a small parcel rather than a large letter, which costs more. If your product is close to the limit, tell us when ordering so the box can be made to a size that protects the contents without adding unnecessary depth.

Can letterbox boxes be printed with my branding?

Yes. The lid, sides and inside can be printed with your logo, colours and messages, just like a larger mailer box. Keep the area under the postage label plain so the address and barcode remain easy for postal systems to read.