First, lets talk environment. Exchange 2010 RTM, Windows 2008 R2. Mailbox and CAS are 2010. The mobile device is a Windows Mobile 6.1 - This requires a Windows Mobile 6.1 or better device. No iPhone, no Blackberries have this functionality.
Install Outlook Mobile 6.1 on your WM 6.1+ device - Download from Microsoft at: https://update.outlook.com/cabs/OutlookLiveSetup.cab
Thanks to Mike here for this link: http://evangelyze.net/cs/blogs/mike/archive/2009/10/06/wm-6-1-outlook-mobile-update-for-exchange-2010.aspx
Configure Acticesync to your Exchange 2010 CAS server(s), and the next time you go into text messages, your device will prompt you asking if you want to sync texts with Outlook. When you accept this, you will get an email like this one:
The link for this is: http://help.outlook.com/en-us/140/dd251212.aspx
When you log into OWA (or Outlook 2010 when available) you can send texts to contacts from OWA:
Exchange uses Activesync to instruct your device to text on your behalf.
When a reply is received to your phone, the next activesync (aka, when you get an email) will pull that text into your inbox:
Users can disable/turn off/edit this feature in OWA options:
Of course, this can be disabled entirely for all users of a CAS server using:
Or this can be disabled per user using new Exchange 2010 OWA Mailbox Policies!