Great tips for allowing pre iPhone 3.1 OS to connect to Exchange Activesync.

Many Exchange Server customers have reported issues logging on to Exchange using iPhone devices older than iPhone 3GS. iPhones support Exchange ActiveSync (EAS), the same protocol supported by Windows Mobile devices, and licensed by many other mobile device manufacturers.

Exchange Server 2007 SP1 and later support many additional policy settings. Two policy settings that are of interest here are:

1. Require device encryption: When you enable this policy, mailbox data synchronized and stored to a mobile device is encrypted.
   
   Fig 1: Exchange ActiveSync policy requiring device encryption
2. Allow Non Provisionable Devices: You can disable this setting (default) to prevent provisioning of devices that can't fully apply Exchange ActiveSync policies.

The iPhone 3GS supports device encryption, and is the first version to do so. Previous iPhone models, including the iPhone 3G, do not support device encryption. Additionally, before iPhone OS 3.1, these devices did not communicate their policy status correctly, resulting in the devices being able to connect to Exchange Server, even if your Exchange ActiveSync policy required device encryption and did not allow non-provisionable devices.

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You Had Me At EHLO... : Exchange ActiveSync and iPhone OS 3.1