ShippingEasy

It's a very good app. The only drawback is that it does not accommodate FedEx Smart post and this is critical for us. It was once a great one stop shop for 2 of our online stores, 1 in 3dcart, the other in shopify. Without this compatibility we have to manually process orders in a separate FedEx module which adds a lot of time. Will be looking for a different one stop solution to get the efficiency I want. If you do not use Smart Post, it is the best shipping app there is IMO.