External Email in Exchange, how can user access outlook?

I have a user that authenticates to our domain but does not need internal email (@mydomain.com), but still he wants to use outlook so he can view the public calendars.  Is there anyway he can still use the internal calendars without giving him internal email?  

I have configured his AD account as an external smtp email, but when I go into outlook it asks me to authenticate to that domain - which we don't want him to get into his email that way.  We only set him up with an external smtp email address so internal users can see him on the email list and it will email his outside address and i can place him into email groups.
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kind4meConnect With a Mentor Commented:
Taking from http://www.experts-exchange.com/Software/Server_Software/Email_Servers/Exchange/Q_21473457.html
Can't be done.
For access to Public Folders requires Outlook configured, which requires a mailbox. Therefore you will need to create a mailbox in order to configure Outlook.

I have found the same.  
tootsie_rollAuthor Commented:
Thanks for the help.  I was hoping for a better answer-obviously not your fault!! :)
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