How to Ship with Poly Mailers on Palmstreet
What is a Poly Mailer?
A poly mailer is a lightweight, waterproof plastic shipping bag made from polyethylene. It’s flexible, tear-resistant, and seals with a self-adhesive strip, making it a popular packaging choice for soft, non-fragile items like clothing and accessories.
Because poly mailers weigh almost nothing and take up very little space, they can significantly reduce your shipping costs compared to cardboard boxes.
When Should You Use One?
✓ Good for
Clothing (T-shirts, dresses, leggings)
Accessories (scarves, belts, hats)
Cosmetics and small beauty items
Books and magazines
Plush toys and soft goods
× Not suitable for
Glassware or ceramics
Electronics
Anything fragile or rigid
Items that need to hold their shape in transit
Common Poly Mailer sizes
Choose a mailer that fits your item snugly when flat. Use the empty mailer’s dimensions, not the packed size, when filling in length and width.
How to Get Poly Mailer Rates from USPS When Buying a Label
Palmstreet currently supports poly mailer pricing through the Custom Rate flow. The key is to enter your mailer’s flat dimensions with a height of 0.25 inches: this small height signals to carriers that the package is a flat soft-pack, which qualifies for lower USPS rates.
Note that UPS and FedEx do not offer special soft-pack pricing; for those carriers, standard dimensional weight pricing applies.
💡 Why 0.25"?
USPS calculates rates for flat soft-pack mailers using only the length and width — thickness is effectively ignored. Setting height to 0.25" tells the system this is a flat mailer, not a box, so you get the correct lower rate automatically when you select a USPS service.
Open the shipment and click Buy Label
From your order dashboard, open the order and click Buy Label to start the shipping flow.
Select the "Custom Rate" tab
At the top of the Package detail section, click Custom Rate. This lets you manually enter your package dimensions.
Enter your mailer dimensions
Fill in the length and width of your empty mailer (lying flat). SetHeight to 0.25". Then enter the total package weight (item + mailer bag).
Select a USPS service and purchase
Choose your preferred USPS service (e.g. USPS Ground Advantage or Priority Mail). Because of the flat dimensions you entered, the rate returned will already reflect poly mailer pricing — no extra steps needed.
📌 Save time with Shipping Presets
If you regularly ship with the same mailer size, save these settings as a Shipping Preset under Store Settings.
Tips to Avoid Extra Charges
Use flat, non-gusseted mailers
A gusseted or expandable mailer has pleated sides that let it expand. Carriers can reclassify these as boxes and apply standard dimensional weight pricing. Always use flat poly mailers to keep costs low.
Don’t overstuff the mailer
If a mailer bulges significantly when packed, carrier scanners will measure the widest point rather than the flat dimensions. This can increase your DIM weight or trigger additional handling surcharges, even if your empty mailer was within limits.
Watch size limits for UPS and FedEx
UPS and FedEx do not have special soft-pack pricing. They bill based on actual vs. DIM weight (whichever is greater), and apply an Additional Handling surcharge to soft-sided packages that exceed these dimensions:
📌 Recommendation
For poly mailer shipments, USPS Ground Advantage or USPS Priority Mail will give you the best rates. Use UPS or FedEx only if speed or coverage requires it.
FAQ
We answer common questions about poly mailers below:
Why do I need to set height to 0.25"?
USPS uses a flat soft-pack formula that ignores height for poly mailer pricing. By setting height to 0.25", you signal to the system that this is a flat mailer rather than a box, which ensures you receive the correct lower rate. If you leave height at 0 or enter a larger number, you may be quoted standard box rates instead.
What weight should I enter?
Enter the total weight of the packed, sealed package: item plus the mailer bag itself. Poly mailer bags typically weigh 0.3–0.8 oz depending on size, so you can round up to the nearest ounce to be safe.
Does this work for UPS and FedEx too?
You can use the same dimension setup for UPS and FedEx, but there is no special soft-pack pricing for those carriers. The main benefit with UPS/FedEx is that a lightweight mailer reduces your actual weight charge.
Can I save my poly mailer settings as a preset?
Yes. Go to Settings → Shipping Presets and create a preset using the dimensions above (e.g. 10" × 13" × 0.25"). Once saved, apply it in one tap when buying any label.
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