David Shipley and Will Schwalbe have written an email style guide, an Emily Post for the cubicle set. I can't abide by the endorsement of excessive exclamation points, but maybe the rest of the book is more useful? Send is available at Amazon.
Apparently, signing off your emails with "Best" is "something close to a brush-off". I sign most of my emails with "Best", especially when I don't know the person particularly well, and I definitely don't mean it as a brush-off. "Sincerely" is too formal, "Warmest regards" is a lie (you can't give absolutely everyone your warmest regards), and "xoxo"...I'm not a girl. So "Best" it is...don't take it the wrong way.
