If you sell online, one of the first packaging decisions you face is simple to ask and surprisingly easy to get wrong: should you use mailer boxes or shipping boxes? Both are made from corrugated cardboard, both get your products to customers, and the names are often used interchangeably. But they are built for different jobs, and choosing the wrong one can mean damaged orders, higher postage or a forgettable unboxing.
This guide explains the difference in plain English, with UK-specific tips on postage sizes, so you can pick the right box for every product you send.
Quick Answer
- Choose a mailer box for light to medium products sent direct to customers, where presentation matters: clothing, cosmetics, candles, books, subscription boxes and gifts.
- Choose a shipping box (a regular slotted carton) for heavy, bulky, fragile or multiple items, wholesale orders and anything that will be stacked in a warehouse or van.
What Is a Mailer Box?
A mailer box is a one-piece corrugated box with a hinged lid, folded side walls and a front tuck flap. It locks together without tape and opens like a gift box, which is why it is the default choice for direct-to-consumer brands.
Mailers are usually made from thin, strong E-flute or B-flute corrugated board with a smooth outer liner that takes print well. You can print the outside, the inside, or both, so the moment the customer lifts the lid is part of your brand experience.
Strengths of mailer boxes
- Self-locking: fast to fold and no tape needed for most styles
- Premium, gift-like unboxing
- Excellent print surface inside and out
- Can be sized to fit UK Large Letter or Small Parcel limits
- Work as both outer packaging and display box
Limitations
- Less suited to very heavy items
- Usually designed for one or a few products, not bulk
- The tuck flap can open under rough handling if the box is overfilled
What Is a Shipping Box?
When people say “shipping box” they usually mean a regular slotted carton (RSC): the classic brown box with four flaps on top and four on the bottom, closed with tape. It is the workhorse of warehouses, removals and wholesale deliveries.
Shipping boxes come in single wall, double wall and even triple wall board, so they can handle real weight. They are cheaper per cubic centimetre than mailers and stack well on pallets.
Strengths of shipping boxes
- Strong enough for heavy or fragile goods
- Available in single, double and triple wall
- Economical for large sizes and bulk orders
- Stack well in vans, warehouses and on pallets
Limitations
- Needs tape to close, which slows packing
- Plain look and less memorable unboxing
- Flaps and tape make them less suitable for printing inside
Mailer Box vs Shipping Box: Side by Side
| Mailer box | Shipping box (RSC) | |
|---|---|---|
| Structure | One piece, hinged lid, tuck front | Four top and four bottom flaps |
| Closing | Self-locking, usually no tape | Packing tape |
| Typical board | E-flute or B-flute | Single, double or triple wall |
| Best for | Light to medium items, D2C orders | Heavy, bulky or multiple items |
| Presentation | High, printable inside and out | Functional |
| Packing speed | Fast | Slower (taping) |
| Stacking | Good for light loads | Very good |
How to Choose: Five Questions
1. How heavy is the order?
Mailers handle most everyday products comfortably. Once orders get heavy, or the product is dense like glass bottles or books in bulk, a double wall shipping box is safer.
2. How fragile is it?
Fragile items can travel in either box, but they need a snug fit and an insert. A mailer with a die-cut card insert is ideal for candles, glass jars and cosmetics; a double wall carton with void fill suits larger fragile goods.
3. Does presentation matter?
If the customer is opening the box themselves, especially for gifts, subscriptions or social-media-friendly brands, a printed mailer turns delivery into marketing. For B2B, wholesale or replacement parts, a plain shipping box is usually fine.
4. Which postage size are you aiming for?
In the UK, carriers price by size and weight bands. Royal Mail’s Large Letter, for example, has strict maximum dimensions and weight, and anything bigger moves into parcel pricing. Many brands design a slim mailer that fits through a letterbox so customers do not need to be home. Always check the carrier’s current size limits before finalising your box dimensions.
5. How many products go in each order?
One or two products suit a mailer. Bundles, refills and wholesale orders often need a larger shipping box, sometimes with smaller mailers or product boxes inside.
Can You Use Both?
Yes, and many growing brands do. A common setup is printed mailers for individual customer orders, plain shipping cartons for wholesale and stock transfers, and product boxes for anything sold on a shelf. Keeping a small range of standard sizes simplifies packing and buying.
Sizing Tips That Save Money
- Measure the product with any inner packaging, then add only a few millimetres each way.
- Use the internal dimensions (length x width x depth) when ordering.
- Avoid paying to ship air: oversized boxes cost more in postage and need more void fill.
- Group products into as few box sizes as possible.
Our guide on how to measure box dimensions explains this step by step.
Printing and Branding
Both box types can be printed, but mailers give you far more space and impact. Popular options are a one-colour logo on kraft for an eco look, full-colour outer print for bold brands, or a plain outside with a printed inside for a surprise reveal. See custom printed boxes and custom boxes with logo.
Sustainability
Corrugated cardboard is widely recycled across the UK, and both mailers and shipping boxes can be made from recycled or kraft board. Right-sizing your box is one of the easiest ways to cut material, void fill and emissions at the same time. A self-locking mailer also removes the need for plastic tape.
FAQs
Is a mailer box strong enough to post on its own?
Yes. Mailers are designed to travel without an outer box, as long as the size and board grade suit the product weight.
Are mailer boxes more expensive than shipping boxes?
Per box, mailers often cost a little more because of the die-cut structure and print. But faster packing, less tape and smaller sizes can offset the difference.
What board should I choose for a mailer?
E-flute suits most light products and gives the best print; B-flute adds strength for heavier items.
Can I order small quantities?
Yes. At Custom Boxes Peak our minimum order is 50 boxes, so you can test a design before ordering in volume through custom boxes wholesale.
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Get the Right Box for Your Orders
Still not sure? Send us your product size, weight and how many items go in each order, and we will recommend the right style and board. Explore our custom shipping and mailer boxes or get a free quote today.
