What I wrote in the last post, about salutations, applies to complimentary closes. I also referred to a 2009 WORDS ON THE LINE post advising how to choose the best salutation and complimentary close in email. In general, the best close ranges from none at all when rushed to Thanks when grateful to My best when hopeful to Sincerely when formal.
A final suggestion: let your organizational culture guide you. Notice how respected employees in your company close their messages and follow suit. If you run a single-person or small business like me, then notice how the good writers among your clients and vendors write. Chances are you'll choose well.
