The OWA external test uses the Test-OwaConnectivity cmdlet to verify that Microsoft Office Outlook Web Access is running as expected by testing the external OWA URLs
<ClassType ID="Microsoft.Exchange2007.Synthetics.CasTX.Owa.External" Accessibility="Public" Abstract="false" Base="Microsoft.Exchange2007.Synthetics.CasTX.Owa" Hosted="true" Singleton="false"/>