Configuring Exchange 2007 accounts with Apple Mail 5, Contacts and iCal (bundled with OS X 10.7 Lion)
Go to System Preferences
Go to Mail, Contacts & Calendar
Select Microsoft Exchange
Fill in your Full name, your Email Address and your domain password
You will be prompted to verify certificate. You can ignore this for now and hit continue.
Replace the User name with your CAIR\ domain credentials. The Server address is weboutlook.du.edu.
You will receive a confirmation screen.
Select the services you want to synchronize.