Why send an email? Say it with Notes!
I think this is a very underutilized tool in Photoshop. You have the option to place sticky notes in an image with the Notes tool (N). When you double-click on the note, it opens up to reveal any content. This allows you to give people direction and be very specific about it, instead of saying "Change the section to the right of the image above the head near the left 1/3 of the section of the eyebrow." Put a note on it, and you're done.