letterbox boxes

letterbox boxes are slim postal boxes designed to fit through a standard UK letterbox so orders can be delivered when nobody is home. Custom Postal Boxes makes letterbox boxes to order in Wolverhampton, sized to stay within Royal Mail large letter limits, with custom print, low minimum order quantities, free design support and free UK delivery.

Why letterbox boxes reduce failed deliveries

A parcel that fits through the letterbox removes the most common cause of failed delivery, which is a customer being out. There is no doorstep exposure to weather or theft, no card through the door and no trip to a collection point, so the order simply waits on the mat. For subscription and repeat purchase brands, that reliability is a strong reason to choose the format, as shown by ranges such as letterbox postal boxes and large letter postal boxes.

The trade off is depth. Everything, including the product, its inner packaging and the box walls, must fit within a slim profile, so product choice and packing discipline matter more here than with a standard parcel box. Flat, flexible or compressible products suit the format best.

Royal Mail limits for letterbox boxes

Royal Mail large letter format allows a maximum length of 353 mm, a width of 250 mm and a thickness of 25 mm, with a weight limit of 750 g for most services. Those figures describe the finished packed item, so the box itself must be shallower than 25 mm once its board and any bulge from contents are counted. Checking your packed sample against the Royal Mail size information for tracked services before ordering in quantity prevents a costly band mistake.

Letterbox size versus postal size

A box can meet the large letter limits and still fail at a narrow or stiff letterbox flap, so test through a real letterbox as well as against the postal measurements. Standard UK letterbox apertures vary by door age and style, and a box near the maximum width needs a smooth surface and square corners to slide without catching. Slightly undersizing the footprint gives a margin for both checks.

Keeping the packed depth under control

Depth is lost in small places, including thick tape, overlapping flaps, a bulky label backing and contents that spring back after packing. Lay flat products flat, avoid stacking two rigid items at the centre where bulge is greatest and press the closed box gently to confirm it stays slim. If the lid rises after packing, the contents need rearranging, not more tape.

Products and packing that suit letterbox delivery

Clothing, books, documents, beauty refills, pet treats, craft kits and boxed teas are among the many products that travel well in this format. Corrugated board protects against bending far better than a bag or envelope, which matters for printed materials, greetings cards with added gifts and flat packed items that must arrive crisp.

Print and branding on a slim box

A slim box still offers two large flat faces for branding, and the top face is seen the moment it lands on the mat. Keep the delivery label area clear in your artwork and use the remaining space for your logo, a short message and reorder details. Inside print is visible as soon as the box opens, even though the box itself is shallow.

Ordering letterbox boxes from Custom Postal Boxes

Tell the team your product dimensions and target postal band through the contact page for a quote and pricing will reflect size, material and quantity, with free design support included. You can also look at A5 postal boxes and C4 postal boxes for named paper sizes, or read the related tag page on Royal Mail small parcel boxes when some orders grow beyond large letter depth.

FAQs about letterbox boxes

What size are letterbox boxes allowed to be for Royal Mail?

For large letter format the packed item must be no more than 353 mm long, 250 mm wide and 25 mm thick, and no heavier than 750 g for most services. Those limits include the box and all of its contents.

Will a letterbox box fit every UK letterbox?

Most standard letterboxes accept this format, but apertures vary and stiff flaps can resist wider boxes. Testing a packed sample through a real letterbox is the safest check before a full order.

What products suit letterbox boxes best?

Flat or compressible products suit the format best, including clothing, books, documents, beauty refills and craft kits. Rigid or bulky items usually need a small parcel box instead.

Can letterbox boxes be printed with my branding?

Yes. Both outer faces and the inside can be printed, as long as the delivery label area is kept clear in the artwork. Print does not change the depth when it is applied as part of the board finish.