If you are unable to setup the Autodiscover CName you can follow the steps below in order to connect with Exchange 2010.
MIGRATION - NEW CLIENTS - We RECOMMEND setting up the Autodiscover cname during the migration. The cname will not affect the incoming mail settings with the other hosted provider. You do not need to alter the MX Record settings until the very end of the migration.
1. Run the Exchange 2010 New Profile Connector script located at the bottom of this page.
2. Restart Outlook.
3. Outlook prompts for user and password.
4. Outlook re-prompts for password.
5. Outlook prompts with a message unable to connect to Exchange, select OK.
6. Outlook prompts to retry to connect to server or work offline, Select work offline.
7. Outlook prompts for user and password.
8. Outlook prompts for user and password.
9. Outlook prompts, 'user can't be resolved'. The box displays server na01.msexchangeoutlook.com and full user name.
10. You will be required to add the server name your mailbox resides on (e.g. exch001sv2. it should appear as exch001sv2.na01.msexchangeoutlook.com) to the server name and click check.
Note: The server address can be found within OWA using Internet Explorer > Click the ? in the top right hand corner > About > Mailbox Server Name:
11. Outlook will prompt unable to resolve user, select check.
12. Outlook will prompt again, unable to resolve user click check and apply.
13. Outlook will prompt unable to resolve user click check and on the forth check it resolves the user, select OK.
14. Outlook prompts unable to reach mailbox. Click OK. Outlook then closes.
15. Re-open Outlook, Outlook prompts for username and password click OK. Outlook prepares for first use and retrieves mailbox data.