Label error — SEKO EasyPost — Malformed syntax

SEKO EasyPost label error caused by missing or invalid customer contact details, usually a missing or incorrectly formatted phone number.

1 min readUpdated Oct 1, 2026

This error occurs when SEKO EasyPost cannot create a label because of missing or invalid customer contact details, most commonly a missing or incorrectly formatted phone number.

Error message

"SEKO API returned errors: Failed to create shipment. [EasyPost_Error: The request could not be understood by the server due to malformed syntax.]"

What this means

SEKO EasyPost rejected the request because customer contact details are missing or invalid. This is most commonly a phone number issue — either missing, or with an incorrect number of digits for the country.

How to fix it

  1. Open the RMA.
  2. Review the customer's contact details.
  3. Add a phone number if one is missing.
  4. If a phone number is present, check it has the correct number of digits for the country. For US returns, use a 10-digit phone number.
  5. Regenerate the label.

If the issue continues

Contact support with the RMA ID and a screenshot of the error.