Pirate Ship offers great USPS discounts—up to 87% off—and makes printing labels...

https://research-wiki.win/index.php/Shippo_vs_Pirate_Ship:_Which_One_Has_Better_Integrations_for_Marketplaces%3F

Pirate Ship offers great USPS discounts—up to 87% off—and makes printing labels easy, especially for small shops. But if you need DHL Express or faster, live chat support, Shippo might suit you better