The Microsoft Outlook Team announced April 29 the addition of add-ins Uber, Boomerang and PayPal, among the first partners to bring add-ins that can be
accessed without leaving Outlook to Outlook.com’s 400 million active users.
New unified consumer and commercial Outlook APIs were also announced, and create an open platform for developers to build contextual experiences for Outlook.com and O365 users.
Developers can build add-ins with open standards such as HTML, CSS3 and JavaScript for user interfaces, with the option to integrate further using REST APIs and OAuth for secure access to data and services. Details on how to request an account are available here.
Add-ins can be used worldwide across Outlook.com, Outlook 2013 and the Outlook Web App.