Unity Express (UE) is software and comes installed on Cisco hardware that you have choices with. One is an AIM module which is a daughter card that plugs on to the motherboard on the ISR routers (2800,3800).
The second UE option is a Network Module for the ISR routers (NM-CUE). The third is a NM-CUE-EC which again has more capacity along with the fourth NME-CUE which is the top end hw wise.
Unity express integrates well with CME and CCM.
Unity Express Hardware Info:
Up to 14 hours of VM storage - AIM-CUE (50 mailboxes max)
Up to 100 hours of VM storage - NM-CUE (100 mailboxes max)
Up to 300 hours of VM storage - NM-CUE-EC (250 mailboxes max)
Up to 300 hours of VM storagae - NME-CUE (250 mb max)
The difference between NM-CUE-EC and NME-CUE is that NME-CUE has 24 concurrent connections from UCM or UCME where NM-CUE-EC has 16). FYI NM-CUE has 8 and AIM-CUE has 6.
** Be aware the AIM-CUE has some Unity Express feature limitations compared to the NM hardware.
T.38 FAX server integration we use Interstar Xmedius Fax Express. This is an affordable FAX server platform that works very well and doesn't require expensive brooktrout cards.
http://www.faxserver.com/fax-server-software/xmediusfax/express/index.htm
This fax server software would be on a separate server or VMware guest.
HTH
Mike