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.
Context.IO, an e-mail API provider, has announced a "lite" version of its popular Context.IO API. The Context.IO Lite API is not a replacement for the original API. Rather, Context.IO Lite started as a small project to improve Webhook performance. The potential of Lite quickly made itself known, so Context.IO decided to fully develop the Lite version and has now launched a beta version.