A list of Aftership alternative tracking sites1. Trackingmore
If you are looking for a restful tracking API, you can check Trackingmore's API, they support 410 couriers. And the price is much cheaper than Aftership.com. Btw, they also provide a package tracking APP for online buyers.
This is a global tracking site, you can track most of your shipments here, especially for those postal tracking numbers.
Many people use this site, because it support express tracking as well as air cargo tracking.
Other alternative sites:4. track24.ru