Just use code words. My family has been doing it for years. The volume of email traffic is so much that they would have to use programs that key in on certain words or phrases. They would then need a human to cipher thru all the garbage.
Sarin, plutonium, Pentagon, White House, bin Laden.
Oops, this is the Obama administration. New suspect words must be used:
Freedom, liberty, second amendment, Constitution, birth certificate, America.
“Just use code words.”
Navajo code words, of course!
(Actually, I’d go for a more obscure language.
“It is estimated that 6,809 “living” languages exist in the world today, but 90% of them are spoken by fewer than 100,000 people.” http://en.wikipedia.org/wiki/Indigenous_language
I’d also pick a decoy language and send, from an autonomous, very remote server, messages in that language sprinkled with words & phrases designed to trip the NSA alarms.
Just to yank someone’s chain, of course. Mix in a few Arabic or Farsi phrases as Red Herrings.
(oooooh, I’m getting WAY too much enjoyment out of devious planning!)