The CRM App for Outlook was a preview feature for CRM 2015 Online Update 1 only available in North America. As of CRM 2016 Online Update it is a supported feature.
The CRM App for Outlook works with Outlook 2013 or Outlook Web App (in Office 365) and is different from the CRM client for Outlook.
Some of the requirements inlcude:
- Must use Exchange Online for email processing
- Must use server-side synchronization
- Must add the CRM App for Outlook to the Exchange Online service
More details at https://www.microsoft.com/en-us/dynamics/crm-customer-center/crm-app-for-outlook-user-s-guide.aspx and http://blogs.msdn.com/b/crm/archive/2015/12/10/the-new-light-weight-crm-app-for-outlook.aspx