Possibility to prevent Mail-Sync via EAS

Hi,

one of our customers defined a requirement to prevent Mail-Sync via ActiveSync.
They only want to allow sync of Calendar and Contacts to mobile devices.
Unfortunately they don't have a MDM-solution.

They use Exchange 2013.

I checked the Cmdlets Get-MobileDevicePolicy, Get-ActiveSyncVirtualDirectory, Get-CasMailbox, Get-Mailbox for related Attributes, but there are no options which do the work.

Is there any option i missed?

Regards,
Thomas