I am a the Exchange admin for a medium sized business (150 seats). We have half a dozen Windows Mobile phones that work correctly with Exchange ActiveSync (Exchange 2003). They frequently get heartbeat intervals of 1800 or higher. I have found that iPhones won't even register for AUTD (ActiveSync) if the MinHeartbeatInterval registry key on the server is set to anything higher (sorry I miss-typed it in the title) than 300. What I mean is that the iPhone won't create the AutdState.xml file in the NON_IPM_SUBTREE ( Code: https://exchangeserver/exchange/username/NON_IPM_SUBTREE/Microsoft-Server-ActiveSync/iPhone/Applxxxxxxxxxx/ ) folder. This means that the device will check for new data on manual syncs only but will not receive any push data since it is not even trying to keep a connection open. Has anyone else seen anything like this? Am I doing something wrong.