Within ShipStation, it is possible to ship First Class Mail Domestic Packages weighing up to 15.99oz. Packages 16oz or higher will require you to choose a non-first-class service.
- Select USPS First Class Mail from the Service drop-down menu
- Select the appropriate package type from the Package drop-down menu (for custom or non-standard packages, simply choose Package).
- Enter the weight (or click the scale icon if using a scale and ShipStation Connect)
- Get the rate
- Create Label
Stamps.com accounts connected to ShipStation currently allow a maximum value of 15.99oz, and Endicia currently allows a maximum value of 15.9oz for First Class Mail Domestic Packages. For other details or restrictions for First Class Mail, please refer to the USPS website.