We let the author know. We're not going to lie about a manuscript's potential just to retain an author's business. We believe in candor and honesty, and will be clear with you about the strengths and weaknesses of a manuscript. "Unpublishable" manuscripts, while rare, are the least pleasant part of our job, but we do turn down projects for editorial work past the Evaluation stage if we see them as unlikely prospects for publication even with the benefit of editing. At the same time, we also offer a clear and comprehensive explanation of the challenges we perceive and what the author can consider to get the manuscript on a better track.