With Exchange 2013, Microsoft has introduced a new feature called Office Apps.

Office Apps is providing a new way to develop for Exchange 2013 (as well as for SharePoint 2013) in order to provide additional functionality to end-users through Outlook 2013 client or Outlook Web Access (such as a map to locate a location when you receive a request meeting) – to know more about Office Apps see http://blogs.msdn.com/b/officeapps/archive/2012/07/17/introducing-the-new-office-cloud-app-model.aspx

With Exchange 2013, and also with Exchange Online 2013, there is some apps provided and enabled by default.

You can off course disable these apps (see http://blog.hametbenoit.info/2012/09/23/exchange-enable-apps-for-all-users/) but this doesn’t disable the possibility for end-user to add and install their own Office Apps.

To lock down Office App, follow the following steps:

On Premises

• From an Exchange 2013 server, launch the EMS (Exchange Management Shell)
• Run the following CMDlet Set-OrganizationConfig -AppsForOfficeEnabled $false

Exchange Online 2013

• Launch Microsoft Online Services Module for Windows PowerShell
• Connect to your Office 365 tenant running Exchange Online 2013 and run the previous CMDlet