Work / Signing a contract by email with a large company in Poland [3]

I've been offered a position in Poland by a large international company. They emailed me a scanned version of the working contract that is already signed by them. I'm supposed to print it, sign it, scan it and email it back to them. I'm not residing in Poland at the moment nor have I ever resided there.

My question is: Is this contract valid in Poland and/or is it a common practice? After all we are not signing the same paper. In my native country I believe this kind of a contract would be of a very questionable nature and an original paper copy signed by both parties would be required.

-Samuel