Unsubscribing to emails is not the same as getting off of email lists. Also, you may be on many, related lists. Some with the GS organization and others with organizations they've shared your address with. Emails are not a real problem. I get at least 50 a day I never read; the delete button is your friend.
Snail mail is another issue altogether and again you are probably on many related and some unrelated mailing lists.
For email your easiest and most effective strategy is creating additional folders and direct your unwanted email to the related folder automatically. Then delete them all at once as you want. That way they never get into your primary folder. Most email programs provide for that service.
For snail mail, the wastebasket is your friend.