The Help Scout Ruby Library by Hector Ramos in beta stage helps to access the API features of fetching users, mailboxes, customers, and conversations. API required available at http://developer.helpscout.net/
Our API directory now includes 199 email APIs. The newest is the Uptime Robot API. The most popular, in terms of mashups, is the SendGrid API. We list 10 SendGrid mashups. Below you'll find some more stats from the directory, including the entire list of email APIs.
Email marketing service provider MailChimp announced last week a new $1 million dollar fund for startups building products that integrate with the service's MailChimp API. MailChimp's program is somewhat unique in that they won't be asking for equity from the companies they fund. It's a pretty attractive deal for prospective partners and a trail-blazing move for a platform in an increasingly competitive industry.