An email marketing campaign isn't about the newsletter, but about the mailing list. That's something we all learn pretty quickly once the campaign gets underway. Email subscribers are a valuable bunch. Unlike the one-time-only visitors to your site, subscribers are the ones who keep returning, referring, and most importantly, engaging on an on-going basis. It's that kind of traffic that’s more easily converted. Once you've got subscribers, the trick is to keep them, and get them to interact.