The Dxx Cxxxx Agency thanks you very much for your recent submission. We apologize that the volume of submissions necessitates our replying in a form letter. And while we appreciate your thinking of the agency, we’re afraid that the project you propose does not seem right for our list. Another agency may well feel differently, of course, and we certainly want to wish you the best of luck with your work. Thank you again for the chance to consider your book.

Ya gotta love this phrase, “…for the chance to consider your book” – because the name of the book is NEVER mentioned. That is a nice touch.