Purpose-driven email

I work for a multinational corporation with over 20,000 employees, and the people I work with spend much of their time in meetings (parodied well here: "Hate making decisions?  Hold a meeting!")

It's gotten so it seems like anyone with an ability to move the organization spends their days in back-to-back meetings thanks to a vicious circle that works like this:

1) People receive more email than they have time to read properly (if at all), much less respond to in a timely fashion.
2) On top of the baseline of existing meetings are piled additional meetings to get answers to questions in unread emails.
3) Calendars get filled to the point where some poor souls only have time in their days to prepare for meetings, go from one meeting to another, contribute to those meetings, and follow up on the decisions made in them (typically by scheduling more meetings). 
4) The response rate to emails drops even further, reinforcing the notion that the only way to get something done is to schedule a meeting.

Not that meetings are by nature inefficient.  Humans talk at a rate of over 100 words per minute.  Few people can type an email that quickly.  And clearly the ability to get real-time feedback on what you're saying--especially through visual cues and tone of voice--is invaluable for certain topics and decisions.  But for shorter messages, or where maintaining a written record of the response is essential, email frees all involved parties to choose the time and place to take in the content and react.

I have a suggestion.

Before you send your next email, take a few moments to metatag it with the role of each recipient on your email.  Use metatags to state the purpose of sending each person your message: "For ASAP read and advice/opinion"; "For information"; "For review and approval"; "Urgent action requested"... you get the picture.  If there is a deadline or loose time frame for the named purpose, create a metatag for that, too.

Metatagging complete, your intended recipients can now filter incoming messages to ensure they are reviewed in order of urgency, as opposed to order of arrival. 

The you spend to do this will (a) clarify the desired reaction from each recipient and (b) result in not a few superfluous recipients being removed as senders realize there is no point including them on the email--both small steps in the war against unnecessary email.  And a reduced volume of email, with clearer expectations on what the desired reaction was, will both result in more timely responses and fewer superfluous meetings.

I've been searching for an Outlook add-in that will enable this kind of email tagging.  I've yet to find one. 
Many in business already achieve some of these benefits manually, e.g. by naming their purpose in the email's subject line.  But that doesn't enable them to specify what is expected of each recipient where an email is delivered to multiple colleagues.
My suggestion might not be the solution, but until we find something, legions of corporate movers and shakers will remain shackled to their calendars, trudging endlessly from meeting room to meeting room--pointing sticks, showing charts, and eating donuts.