Force use of Outlook in RDS RemoteApp and iOS Mail and block other forms of mail access

Hi, 

I have setup an on-premise RDS environment for RemoteApps and I have deployed Outlook, Word, SharePoint and PDF viewer.  The environment has also been setup with 2FA.  I would like to force everyone to use the Outlook RemoteApp and block all other forms of connecting to e-mail apart from ActiveSync for iOS.  I'm blocking the Outlook for iOS application already. 

Is there a way that I can block someone from just configuring their outlook application on their desktop computer?  I want to benefit from all the security implemented on this RDS environment but at the moment someone could undermine that by configuring their own outlook client.. 

I am using Exchange 2013 with Outlook 2013.  RDS is on Server 2012 R2. 

Advice is appreciated. 

Thanks

D