I used Experiture for just over a year and they were so-so, not slick and sexy like some other UIs. They're also not as cheap as some of the big guys like Constant Contact or SendGrid. Deliverability became an issue for us so we had to find a new service.
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SquareSpace - Squarespace is the easiest way for anyone to create an exceptional website. Pages, galleries, blogs, e-commerce, domains, hosting, analytics, 24/7 support - all included.
Campaign Monitor - Email marketing software built for designers and their clients to run successful email campaigns.