You can download the beta now from Google Play, if you meet the following requirements:
- Your device is running Android 4.4 Kit Kat or higher
- Your mailbox must be running on Office 365 for business (doesn’t include Office 365 personal, Office 365 Home or Outlook.com)
- Your device size is considered “small” or “normal” by Android OS
Read more here – http://blogs.office.com/2014/06/11/owa-for-android-now-available-on-select-devices/
