You sent an email just now and realized what is wrong with it: content, recipients, sender (are you the right one to respond, in the first place), confidentiality, etc. There are interesting tools that control email before or after it is sent. ComputerWorldUK has an interesting article on some of those tools.
To me, ToneCheck’s sentiment analysis looks nice. That is one application in the right direction. In future, may be we have intelligent auto attendants for all our outbound mails; and they scan for relevance in everything that goes out.