Adding to the Chorus here. We have a newsletter. A substantial number of our contacts want newsletters sent to a non-primary email. Some just have all their newsletters sent to a certain email. Some use various tools to manage newsletters. Some people want the newsletter to go to both their primary and secondary address. So at the moment we have many duplicates in our contact database because of this. Ideally we would like to have a primary address but specify which address(s) the newsletter is sent to.