For an online store, the mailer box is the first physical contact a customer has with your brand. It is also a shipping container that must survive a sorting facility. It has to do both jobs, and getting it right is mostly about three decisions.
Decision 1: Size — the one everyone gets wrong
Oversized mailers waste freight (you pay to ship air and void fill) and look sloppy. Undersized ones crush products or force bubble-wrap armor that hides your branding. The rule: internal dimensions = product dimensions + 5–15 mm clearance per axis, enough for a tissue wrap or a slim insert, no more. If you sell multiple SKUs, it's usually cheaper to run two mailer sizes than one box + half a roll of void fill.
Decision 2: Material and flute
- E-flute corrugated (~1.5 mm) — slim, prints beautifully, fine for light, non-fragile goods (apparel, cosmetics with adequate product packaging).
- B-flute (~3 mm) — the standard e-commerce workhorse; handles moderate weight and stacking.
- Reinforced edges or double-wall for heavy items. Corrugated accepts full-color printing via flexo (economical), litho-lamination (retail quality), or digital (prototypes, short runs).
Decision 3: The unboxing design
The elements that make customers film their mailers: a printed interior (surprisingly affordable — the inside is printed in the same pass), a tissue or sticker seal instead of tape, a printed message on the inside flap ("you made it"), and a removal experience without knives. Keep branding outside too — the parcel travels through the world as an ad, and carriers' barcodes need clear space: leave the label zone unprinted or ask for a laminated label patch.
One warning: the mailer is packaging, not product packaging. If the product itself needs retail-ready packaging later (wholesale, retail chains), plan both from the start — retrofitting retail boxes after launching D2C is a common and avoidable re-spend.
FAQ
Do mailer boxes need to be corrugated, or can they be paperboard?
Light, non-fragile products can ship in heavy paperboard (400 gsm+) boxes, and many fashion brands do. Corrugated is the safer default for anything with weight, glass, or rough carrier handling.
Can I print different designs on inside and outside?
Yes — inside and outside print in the same production pass. Inside printing is the cheapest "wow" available; most factories quote it as a small increment over single-side printing.