ReadReceipt on Active Sync Device
Starting from Exchange 2016, now you can disable Read Receipt Feature on Active Sync Device through cmdlet.
Default Output would be:
Get-CASMailbox <User> | fl ActiveSyncSuppressReadReceipt
ActiveSyncSuppressReadReceipt : False
You can set it $Ture and it will change following option in Outlook Web Access as well.
Set-CASMailbox <User> -ActiveSyncSuppressReadReceipt $True