9696d660_Exchange_Voice_Mail_User_Guide__Description
[Feature] Non-University Phone Numbers [How to Enable or Disable] Send a request to itcom.csr.evm@umich.edu [Description] 
Allows you to log on to your mailbox with just your PIN from one or more additional phones such as your cell phone or home phone. (In other voice mail systems, this is called Direct Phone Access.)
ITS Exchange Voice Mail User Guide
Description