You lost a reader right here - and if I were the person reading this letter it would have gone straight to the shredder at this point:
It is widely assumed by sane and educated people that NSA monitors all email; whether this is true I am not sure, but it is believed.
Believe by WHO exaclty? This sane educated person and most that I know don't really believe this. I would suffice it to say that the majority of the people that believe these conspiracy theories are largely uneducated. Technically speaking this is largely an impractical task as well as it would require coordination with millions of ISPs and email providers worldwide. Now do I believe it does happen in some areas like free mail accounts? Sure. Regardless if it was widespread as to say all email is monitored we would have outrage from many different ISPs world wide.
Tinfoil hats unite!