All iPhone models running 2.x or later firmware are supported. The latest iOS 4 release is recommended. Multiple accounts are available with iOS 4.0 and later. Tasks sync is not supported by the iPhone at present.
iPad and iPod touch
iPod touch devices running 2.x or later firmware are supported with the same features as the iPhone. Because the iPod touch turns off its WiFi network interface when the device sleeps, email won't be pushed. The iPad is also supported. Unlike the iPod touch, iPads keep the WiFi interface powered up when sleeping. Therefore push email works as expected on the iPad using WiFi.
Windows Phone devices run the original EAS client and generally provide the most complete set of sync features of any of the device types except multiple calendars. NuevaSync has a calendar to category mapping capability that allows multiple calendars to be managed on Windows Mobile 6.1 and 6.5 phones (but not Windows Phone 7).
There are several sync clients available for Android devices, all of which are supported. Newer devices generally run Google's own "native" Exchange client. This supports multiple accounts, can sync contacts and push email and in Android 2.2 also calendar events. It does not support tasks sync at present, but the 3rd party client Touchdown does.
All Nokia smartphones are supported. Newer S60 series and S^3 phones come with the Mail for Exchange client installed, or an automated installation wizard. Older devices can get the client from the Ovi store or as a package download. Nokia's N900 Maemo mobile computer has the sync client built-in. S40 Series featurephones are not supported.
All Palm/HP WebOS phones, including the Pre, Pre2 and Pixi are supported. Older classic PalmOS phones such as the Centro are also supported.
Blackberry phones are supported for calendar, contacts and push email sync with the 3rd party (not free) AstraSync application.