Transparent design and clear separation of entities like subscriber, mailing list, newsletter, campaign.
A subscriber is someone from whom you have at least an email address. A mailing list is a grouping of subscribers. A newsletter is the content that you send. Any newsletter can be send in any campaign with any list (or a combination of lists).
Detailed and in-depth reporting on your email campaigns. Comparative and aggregate reports, charts and more.
It's also about your subscribers. You can personalize the whole subscriber experience from "Welcome" to "Goodbye" with custom emails and landing pages. Set-up greeting auto-responder emails and more.