I have a site that I sell social media services on. Over the past year I've made many sales, and now I decided to copy all of the customer emails into an excel file, and from time to time send emails about discounts or whatever - like December New Year discounts, shit like that. What I'm unsure about is whether I should save their Paypal emails, or emails they submitted when ordering (they're often different), or both? At first I made peace in my mind that I'll just save the emails they submitted, not their Paypal emails. But now that I've sat down to do it, I have doubts. What do you guys think?