WARNING: It's clouding your creds & emails
WARNING: This is a rebadged Accompli client. All your account details, including passwords are stored on Accompli servers and a cache of your email as well.
Microsoft have confirmed this in several blog comment replies (read the responses) http://blogs.office.com/2015/01/29/deeper-look-outlook-ios-android/
There's also info in there on how corporates can block the client.
If you use this with your exchange work email, for instance, they now have your (plaintext) password.
Nice one, MS.