From Darwin Magazine: 7 Tips for Getting of Control of E-mail.
If any subject or issue involves more than two e-mails, one party should call the other to resolve the issue by phone.
No junk e-mail, no jokes.
Only send relevant information, which is defined as just what the person needs to know.
Limit CCs (which might be more appropriately named CYA).
Don’t ping-pong with e-mail for a conversation; use the phone.
Deal with it and delete it.
Don’t read every e-mail as it comes in; handle them in batches.
(via: cutting through)