Is there anything similar to TouchDown for iOS? Is there any app like NitroDesk's TouchDown Android email client for iOS?

Just for background info, many companies force you to have the latest version of iOS installed to access Exchange Server, or you can have a secure client like TouchDown. That means you're out of luck if you're on an unsupported phone such as iPhone 2G which cannot have the latest version of iOS and cannot run TouchDown since it's Android only.

EDIT:

I know the latest version of iOS Mail App has similar features to TouchDown. I'm asking this question because some users may have an iPhone 3G which will not be upgradeable to iOS 4.3, hence they will not be able to access Exchange from their iPhone unless there is an app similar to TouchDown available.
how about the iOS version of TouchDown? :-)

http://nitrodesk.com/touchdown/ios/

https://itunes.apple.com/us/app/touchdown-for-ios/id560596861?mt=8