If you have to write more than two short paragraphs to express your feelings to someone (or especially a client) on something that feels important, pick up the phone and talk to the person.

E-mail is wonderful. But too much tone can get lost… too much room for misinterpretation.

Sure, e-mail is easier.

But talking is much more effective.

(Oh, by the way, I always come back to this rule after crafting a 500 word nuanced reply to someone that I never send.)