Pirate Ship offers great USPS discounts, sometimes up to 87% off, making it...

https://technivorz.com/does-shippo-really-offer-strong-ups-rates-compared-to-other-tools/

Pirate Ship offers great USPS discounts, sometimes up to 87% off, making it perfect if you mainly ship with USPS. Their support is email-only, which works if you don’t need quick responses