A USPS shipment fails with a Mail Piece error when the package type is set to Carrier Letter/Envelope but the package weighs more than the USPS letter limit of 3.5 oz. Change the package type to Customer Packaging (or another type that fits the weight) and the shipment will process.

Problem

You process a USPS shipment and it fails with a Mail Piece error. The package type is set to Carrier Letter/Envelope, and the package weighs more than 3.5 oz (for example, 5.35 oz).

Cause

The Carrier Letter/Envelope package type is USPS letter mail. USPS letter mail can weigh no more than 3.5 oz. A package heavier than that cannot ship as a letter, so USPS rejects it. The weight against the letter package type causes the error, not a problem in Shipstore.

How to check: look at the package type and the weight. If the type is Carrier Letter/Envelope and the weight is over 3.5 oz, this is the cause.

Fix

  1. Open the shipment and find the package type (packaging) setting.
  2. Change the package type from Carrier Letter/Envelope to Customer Packaging, or another type that fits the weight and size.
  3. Rate and process the shipment again.
  4. If orders like this come in often, set your default package type so the letter type is not chosen automatically. If you are not sure how, email support@shipstore.com and include your company name.

What you should see

  • The shipment processes without the Mail Piece error.
  • The package type shows Customer Packaging, or the type you picked.
  • A label prints.