Pocket PC MSN “Exchange Messaging”

So today I received my iPAQ HP H4150, and while checking the settings of MSN Messenger I saw this option.
“Enable Exchange Instant Messaging”
Can someone explain what is this?

Exchange IM is a separate service for corporate Exchange 2000 servers, and the client was integrated in with the consumer versions to avoid having to run two different pieces of software.

You’ll see the Exchange IM option in Windows Messenger too.