It's certainly not one eBay allow on their Simple Delivery for Private sellers.
I asked Mr Google about Aquiline here's their answer:
Aquiline is a service that converts Amazon tracking numbers to a different format to be compatible with platforms like eBay, but it is not a delivery company itself. Sellers use it to hide the fact they are drop-shipping from Amazon, which can lead to issues where the tracking says a package is delivered immediately after an order is processed, but the item has not actually arrived yet. Some buyers have reported packages never arriving after using Aquiline, though many believe it's a legitimate service that simply converts tracking numbers and that the original Amazon carrier is responsible for delivery.
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