Is EMS only for shipping from China? Or are they a global company like DHL/UPS/Fedex etc?
And if you'd bought something from someone in Poland, would you be dubious if they said they were sending it via EMS?
Googled it as it sounded familiar. EMS Pocztex. It's kind of a ParcelForce for the polish mail (Poczta Polska), I'm not sure if it was privatised yet or not, but when You went to the PO then You were able to send a parcel with standard mail or using their own couriers the EMS Pocztex. Just like it's here in a post office. You can send it standard parcel or ParcelForce.
Here's a link http://www.pocztex.pl/ google will have to translate it as there is no language options other than polish 😉 I'm pretty sure they do tracking and insurance like any other courier companies.