Similar to its desktop counterpart, Outlook Mobile offers an aggregation of attachments and files stored on cloud storage platforms; a "focused inbox" highlights messages from frequent contacts, and calendar events, files, and locations can be embedded in messages without switching apps.

[5] First released in April 2014 by the venture capital-backed startup Acompli, the company was acquired by Microsoft in December 2014 for over US$200 million.

Acompli was co-founded as a startup by Javier Soltero, the former chief technology officer of VMWare, alongside JJ Zhuang (CTO), and Kevin Henrikson (VP of Engineering).

[7][8] To distinguish Acompli from other recent email startups (such as Mailbox), Soltero decided to target the enterprise market: he felt that such users had been underserved by mail apps with limited or no support for Microsoft Exchange Server, despite its wide use in such environments.

[19] Outlook Mobile is designed for use with Microsoft's Outlook.com and Exchange, but also supports other e-mail services and platforms such as iCloud, Gmail, and Yahoo!

[24] Outlook Mobile temporarily stores and indexes user data (including email, attachments, calendar information, and contacts), along with login credentials,[25] in a "secure" form on Microsoft Azure servers located in the United States.

Concerns surrounding these security issues have prompted some firms, including the European Parliament, to block the app on their Exchange servers.