“This is one-time email only, you were not subscribed to any mailing list – you don’t need to unsubscribe. If this email offended you in any way, recieve my deepest apology.
There was actually no other way how to address you directly. Your email wasn’t harvested by any robot, I personaly visited and enjoyed your website and chose you as a person who might be interested in my [product].”
Yeah, right.
Hey, I got one that said that the other day, too!