A colleague of mine saw my post of how to write emails and commented that I missed the main feature. His rule is:
Emails should be phrased with appropriate keywords so as to be easily searchable.
In other words, instead of expecting your application to adapt to your needs when searching your mailboxes for an email that you wish to recover, you are the one who ought to adapt to the application and provide the words that make search easy.
My email typically has one intended recipient. Should I also keep in mind, as I am writing it, the search program, and imagine that it is looking over my shoulders as I type and gives me advice on my choice of words? Doesn't this strike anyone as a bit twisted?