Some apps in the Store Beta will fail to install or update due to a licensing issue.
In this build, the Mail, Calendar, and People apps may be broken due to a licensing issue with the Store Beta. To get these apps working again, you need to follow these steps:
- Open powershell as administrator
- Run the command Get-appxprovisionedpackage –online | where-object {$_.packagename –like “*windowscommunicationsapps*”} | remove-appxprovisionedpackage –online
- Re-install Mail, People and Calendar from the Store (green tile)
Information taken from here http://blogs.windows.com/bloggingwindows/2015/03/18/windows-10-technical-preview-build-10041-now-available/