For fully functional inbound and outbound fax capability you'll have to purchase a 3rd party fax server from the list of those supported by Unity.
You can currently get inbound fax routing using the T.37 fax capability on several Cisco gateways using the IP Fax Configuration Wizard with Unity - you can check out it's home page complete with training videos here:
http://www.ciscounitytools.com/App_IPFaxConfigurationWizard.htm
We are working on outbound fax capabilities for the same set of gateways but that's going to be a while yet.