Post Greenland's head office and philatelic bureau is located in Tasilaq. It is not the capital of Greenland. In fact, it is only the 7th most populated town in Greenland. It sits on the eastern coast of Greenland which is less populated than the west.
This is marked with "Porto kontrolleret" to the right of the Tasilaq postmark: "postage controlled". I believe this means the sender didn't put enough postage on the envelope. Perhaps the nice 2 DKK stamps was added by the post office.
Thanks for the cover Martin.