I
would pretty much just chunk it in the trash if I got one of those letters. I WOULD consider it if someone stopped by and talked, I liked them, I got a good felling about them, etc.
To be honest, if I got a letter I pretty much would immediately consider it a cop-out and someone who is just trying to save time and not develop a relationship.
About the only way I would think you would have success is if someone really has a "problem" with deer overpopulation etc. and you provided a ton of references, etc.
I personally would fuel up the truck, put on nice clothes, and knock on some doors.