Joan Acocella parses “an epistolary crisis in this country—a shortfall in valedictions, or sign-offs”:
Now come the businesslike phrases: “Very truly yours,” “Best wishes,” “Best.” (Also “Sincerely yours,” where our old “Sincerely” is operating in a new key.) These are all completely O.K., except that, if you use them on a person to whom, while you’re not close, you’d like to show some warmth—the person got your child a summer job, or you want him to—they feel a little stiff. What I do here is pump the words up a bit: “Very best,” “Very best to you,” “My best to you and Susie,” etc. The “my” makes a difference.
Most of the time, what I’d really like is to say nothing at all: no hello, no goodbye, just the message. While what I’ve said so far applies to both letters and e-mails, the headless, footless message usually turns up only in e-mail. And it will probably be deployed only with intimates. You may also use it, though, when you’ve never met your correspondent but you feel as though you have, because the two of you have spent all day trying to set up a meeting or something like that. You start out “Dear Ms. Smith” and “Best, John Doe.” By the third message it’s just “So how about 3:30 at Starbucks?”
The Dish 