Mailchimp-Quality Mass Email Platform

I want to bring a brand-new, web-based mass mailer to market—something agile enough to rival Mailchimp yet lean enough for rapid iteration. This project is more than a build-and-handoff; I’m looking for... (Budget: £250 - £750 GBP, Jobs: API Development, Email Marketing, Graphic Design, HTML, PHP, SaaS, Web Development, Website Design)