Hi,
Yes, you can have multiple Unity servers connected to one Domino server.
As far as co-location is concerned, I guess it depends on your network. According to the Unity System Requirements doc:
"For new installations, a minimum network bandwidth of 100 Mbps between the Cisco Unity server and the servers listed below."
The following docs have more details that might help you out:
System Requirements for Cisco Unity Release 7.x
Network Requirements
http://www.cisco.com/en/US/docs/voice_ip_comm/unity/7x/requirements/7xcusysreq.html#wp494986
The Unity Design Guide chapter "Network Infrastructure Requirements"
http://www.cisco.com/en/US/docs/voice_ip_comm/unity/5x/design/guide/5xcudg030.html
Designing a Cisco Unity System with Domino as the Message Store
http://www.cisco.com/en/US/docs/voice_ip_comm/unity/5x/design/guide/5xcudg050.html
Nancy
