Checkout: USPS (US Postal Service)
The WordPress Shopping Cart plugin has the USPS shipping rate calculation API version 4 built into it to calculate US Postal Service rates on the fly as your customers checkout.
You need to register for a USPS web tools account in order to get a username/password and then you’ll create the USPS shipping method in the plugin. Follow these steps:
1. Register a USPS Web tools account
Go to the USPS Web tools registration where you will fill in your credentials to create your free, developer USPS Web tools account. This will be a test/developer account.
Once you’ve registered, you will shortly thereafter receive an email from USPS with your username and password to be used with the API. You can use these with the plugin but we recommend that you switch it to a production account.
To switch it to a production account, contact USPS on either the email or phone number below and provide them with your USPS username given in the email so that they can switch it to a production account.
2. Add USPS Shipping Method
You’ll now add the shipping method in the plugin by going to Checkout > Shipping Methods and then click the ‘Add New‘ button at the top to create a new shipping method.
Choose your account type (test/production), fill in your username and password and the origin/warehouse zip/postal code and you’re set to go.
International Mail Type:You will now be able to select an international mail type for international services and a container for all other services except First Class.
Container & First Class Mail Type: You can overwrite the container and First Class Mail Type per product Checkout>Products
Here are some things you may want to check if you have problems: