Exhange 2013 cu2 enabling exsiting AD users as mail users using powershell

we have AD user list as csv file and want to enable them as mail user (with external email address without mailbox) want achive it through powershell.

below link refers for contact wereas we reuire for existing users.

http://technet.microsoft.com/en-us/library/bb684891(v=exchg.141).aspx

Please suggest.