Targeting Apple Native Mail (iOS) with New-ActiveSyncDeviceAccessRule

Hello! We are currently attempting to deploy a massive amount of iOS Based Devices for O365-GCC. MS Authenticator and Outlook for iOS work perfectly together now that Modern Auth is seamless for us, however, I need to be able to target Outlook for iOS and Apple Native Mail; and block all other clients using the Device Access Rules. 

We currently have the default as block, access for Outlook for iOS enabled, but what User Agent String do I use to target Apple Native Mail specifically? I would consider a Device Type Rule (such as, allow iOS), but I don't want any other third party iOS Agents to be able to use it. 

Reference: https://docs.microsoft.com/en-us/powershell/module/exchange/devices/New-ActiveSyncDeviceAccessRule?view=exchange-ps

Thank You,

Bryan