Ask HN: Previous article where the author AB tested his ending email statement

I'm trying to track down the article, but for the life of me can't remember what it was titled.<p>The premise was that the author upped his client responses by changing how he ended his initial contact emails. For example, if I recall correctky, he moved from writing "Let me know if there's anything I can do for you," to something much more directed (i.e. "This is the next step we should take").<p>Does anyone recall this article?