Exchange 2010 and Apple Mail

I have an issue where a user send mail vi Apple' s Mail App but the message does not appear in the "Sent Items" if I have the user use OWA or Outlook on his mac (10.6) he will be able to see all the mail that was sent. I have gone as far as to delete all the mail prefs in Apples Mail program and re-set up Mail an his profile in within Apples Mail program.. Has anyone had this issue?

The Exchange server is running 2010 The users machine is a macpro with 10.6.8 I am not sure what version of the Mail program he has..

Thanks all