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Home > Guides > Shipping in a Plastic Bag
Not a loose one. Carriers reject packages wrapped in ordinary plastic bags like garbage bags, because they tear, snag in sorting equipment, and labels will not stick to them. What works is a poly mailer: a bag engineered for shipping, with sealed seams built to survive the trip.
One scope note up front: LetterAgent's shipping labels are Canada Post Xpresspost, Canada-only, with a 5 kg maximum. Packaging rules come from the carrier, and the guidance below applies across the major carriers.
Three practical reasons. First, a garbage bag or grocery bag tears. It is thin film designed to hold trash for a day, not to survive conveyor belts, drops, and compression under other parcels. Second, loose plastic snags. Sorting equipment is full of belts, rollers, and diverters, and a flapping bag edge catches on them, which can jam the machine and shred the bag. Third, labels do not stick to flimsy plastic. A shipping label needs a flat, stable surface; on a wrinkled bag it peels, folds, or becomes unreadable, and an unreadable label is a lost package. A counter clerk will refuse the bag, and if it somehow enters the system, the carrier can repackage or discard it at your expense.
| Poly mailer | Ordinary plastic bag | |
|---|---|---|
| Material | Thick polyethylene made for shipping | Thin film made for trash or groceries |
| Seams | Heat-sealed, tamper-evident | Tied, taped, or knotted shut |
| Label surface | Flat panel the label adheres to | Wrinkled surface labels peel off |
| Tear resistance | Resists punctures and stretching | Tears on corners and edges |
| Carrier acceptance | Accepted everywhere | Rejected |
A poly mailer looks like a plastic bag to a casual glance, which is where the confusion comes from. To a carrier, it is a different product: thicker, sealed rather than tied, and designed so a label stays put and the contents stay inside.
Sturdy, sealed, and labeled. That is the whole rule, phrased three ways. The package must protect its contents through normal handling, stay closed without relying on the carrier to be gentle, and present a flat surface for the label. Boxes are the default because they do all three easily, but poly mailers, padded mailers, and tubes all qualify when used for the right contents. What does not qualify is anything improvised: bags tied with string, items wrapped in a towel inside a bag, boxes held together with hope. If your packaging looks like it might not survive the trip, the clerk is allowed to say no.
Poly mailers are the budget answer for soft goods: clothing, fabric, documents, anything that does not break. They cost a fraction of a box, weigh almost nothing (which keeps postage down), and every major carrier accepts them. Buy them in the size you actually ship rather than one giant size; a mailer much bigger than its contents leaves loose film that snags, which is the same problem as a garbage bag in miniature. Seal the adhesive strip fully, press the label onto the flat panel, and you have packaging that costs very little and never gets refused at the counter.
Ready to ship it? Get a shipping label with LetterAgent: describe it to your AI assistant, approve the exact quoted price, and get your label.
LetterAgent is a working name. Prices include print, postage, and our service fee. US prices in USD, Canadian prices in CAD (Canadian prices exclude applicable sales tax, added at checkout). Currently in private testing.
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