iPhone Setup for Mail, Calendars and Contacts:

1.  Go to Settings,

2.  Select Mail, Contacts, Calendars > Add Account

3.  Select Microsoft Exchange,

4.  Fill in Email, Username (full email address), Password and Description. 

5.  Click "Next" and it will verify.  

6.  It will add ask for a new field called "Server", type in m.google.com, click Next, Done.

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If you encounter any problems, please try these instructions to configure other specific email applications:  

https://mail.google.com/support/bin/answer.py?answer=75726