I wish I could recycle all the time I spend throwing out junk mail. If there were a conspiracy to befuddle the masses, junk mail would be one of the most insidious weapons in the arsenal. Target the population with stealth junk covered with words like "important", "last chance!", and "personal", preoccupy people's minds with semi-appealing offers, encased in envelopes whose recyclability is perpetually in question. If the conspiracy is successful, people will become deadened to all that claims to be important, personal or opportune. As our minds turn to jello, the nation will falter as it fails to respond to real crises and opportunities.
So I offer this tidbit as a public service, in defense of our great nation and its precious reserves of grey matter. Will the windows contaminate the paper recycling process? A NJ Dept. of Environmental Protection staffer who lives the business of recycling day in and day out tells me the plastic windows float to the surface in the vat of recycled paper fibers and can easily be skimmed off.
So toss those peskily windowed envelopes straight into the recycling bin, and save your quandaring for greater things.