Endicia is part of a larger family including Stamps.com, ShipStation, ShippingEasy, Packlink, ShipWorks and a few others I can't recall off the top of my head.
It's very common to see alerts that packages are coming from Endicia, just like it's common to see a package is coming from Stamp.com.
Put the tracking number into your email search. If you got an email from the company that shipped it, you may be able to make the connection.
If not, you get a surprise when the package comes in the mail.
