Managing communications efficiently

The project management book of knowledge (PMBOK) offers some tips on how to improve communication. Why do we forget these ideas? 

PMBOK highlights:

• Message -- what you want to communicate
• Medium -- the way you send the message and
• Noise -- things that interfere with comprehension.

For email communications, i would add:

• Action Required 
• And what marks this message as complete.

There is nothing more inefficient than exchanging information and one party is waiting or expecting the other to perform some type of action.
On the other hand, i have to be honest that having Action required in email subject lines makes some people uncomfortable, but i feel it's better to be uncomfortable than inefficient.