I save pretty much every email from a potential candidate. That way, when I do need to fill a particular position I can just scroll through the collection of names and books and links I have and quickly (key word: quickly) see who might be a fit. All too often, I come across a note from someone from a year prior who I don't remember and there is nothing in their note that indicates writer or art director.
Sometimes I don't have the time to click through the link and locate your resume and figure it out. Make your position part of your email signature, it's so easy and oh so helpful.