Rebelmail publicly launched its interactive email API. After successful private integrations with ESPs like Mailjet, SendGrid, and others; Rebelmail is ready for third party integrations across the board. Through the API, users can build, send, and track interactive emails directly within an app.
As a developer, you can figure out how to make your program connect to Facebook, Twitter, SMS, and Email. Or you can use the Embarke API and connect just to Embarke, a messaging platform that connects you to them all. You can skip learning the specifics of how to connect to each of them. The REST API's website has a five minute tutorial video on how to use this gateway to its developer tools for social communications.