iphone 4 sync with exchange 2007

My CEO just got an iphone4 and whats it to connect to our exchange 2007 server.  I put in all of the info into the phone but it tells me "unable to verify account informaiton".  Is there something that I need to configure on the exchange server.
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Is activesync enabled for the account and the port forwarded on your router/firewall.
Fridolin MansmannMaster of Business Engineering ManagementCommented:
On the Exchangeserver Active Sync must be configured, certificate installation on iPhone also


see also other resources on the web, e.g. http://www.tipb.com/2008/07/13/walkthrough-exchange-activesync-on-your-iphone-20/
The iPhone uses Exchange ActiveSync to sync OTA. Exchange ActiveSync must be configured on the Exchange server for this to work. Please see the following for more info.


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from: http://www.experts-exchange.com/Apple/Hardware/iPhone/Q_24641648.html?sfQueryTermInfo=1+10+2007+30+4+exchang+iphon

Here are a few steps:
Turn Off Wi-Fi

Tap Settings, Mail, Contacts, Calendars 
Under Accounts tap Add Account& 
Tap Exchange 
Enter your email address, username (in the form DOMAIN\username) and password
Ensure SSL is on
Set the Server field to exchange.mydomain.com

Also if it is still prompting for credentials, open AD Users and Computers, right click the user you are trying to sync and go to the properties > Move to the Accounts Tab and check the Field for 'Logon'.
Make sure you are typing in the same domain name while configuring the iPhone.
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