Or, at least, I’m surprised that this earlier implemented solution has not been mentioned in all the discussion about NSA spying.
Richard Stallman invented an approach to obviating the NSA’s attempts to spy on email. He included it in emacs, the world’s greatest text editor. Here how it works, from the manual. The “M” is the “alt” key (for all practical purposes) and “M-x followed by a word implements the command attached to that word.
32.6 Mail Amusements
M-x spook adds a line of randomly chosen keywords to an outgoing mail message. The keywords are chosen from a list of words that suggest you are discussing something subversive.
The idea behind this feature is the suspicion that the NSA1 and other intelligence agencies snoop on all electronic mail messages that contain keywords suggesting they might find them interesting. (The agencies say that they don’t, but that’s what they would say.) The idea is that if lots of people add suspicious words to their messages, the agencies will get so busy with spurious input that they will have to give up reading it all. Whether or not this is true, it at least amuses some people.
You can use the fortune program to put a “fortune cookie” message into outgoing mail. To do this, add fortune-to-signature to mail-setup-hook:
(add-hook ‘mail-setup-hook ‘fortune-to-signature)
You will probably need to set the variable fortune-file before using this.
 The US National Security Agency.
That is from the current, on-line emacs manual but it also appears in my hard copy of the manual which I believe dates to the last quarter of the 20th century.