Exchange 2013 iApp - Block Activesync except from one IP

Have only used the iApp templates with their defaults in the past but now I'm needing to allow only one IP to ActiveSync to it. We are using MobileIron for mobile devices and I want to only allow MobileIron to talk to the F5 for ActiveSync traffic. I believe they will be pointing their MobileIron server to the F5 VIP.

Any easy way to do this? I've seen one post with code for an iRule to 'block' all activesync traffic but not allow only one IP.

This is what I was referring to:

when HTTP_REQUEST {
    switch -glob -- [string tolower [HTTP::path]] {
        "/microsoft-server-activesync*" {
            drop
        }
    }
}