Hi Slava,
Just to add a note to the good info from Matthew (5 points for your good work Matthew) This interface is only used in CCM to Legacy VM integrations (via SMDI) if you are not setup that way this is why you are seeing this :)
Cisco Messaging Interface Service
The Cisco Messaging Interface allows you to connect a simplified message desk interface (SMDI)-compliant external **Third Party** voice-mail system with the Cisco CallManager. The CMI service provides the communication between the voice-mail system and Cisco CallManager. The SMDI defines a way for a phone system to provide a voice-mail system with the information needed to intelligently process incoming calls.
Genrally the Cisco Messaging Interface (CMI) is a Cisco CallManager service that should be run only on the publisher server. This service intercepts calls destined for voicemail and generates appropriate SMDI messages, which are then delivered to one of the server's Component Object Model (COM) ports.
But can be setup this way,
Cisco Messaging Interface Redundancy
Most voice-messaging systems that rely on an EIA/TIA-232 serial cable (previously known as a RS-232 cable) to communicate with phone systems only have one serial port. You can achieve Cisco Messaging Interface redundancy by running two or more copies of the Cisco Messaging Interface service on different servers in a Cisco CallManager cluster and using additional hardware including a data splitter that is described later in this section.
Each copy of Cisco Messaging Interface connects to a primary and backup Cisco CallManager and registers to the Cisco CallManager by using the same VoiceMailDn and VoiceMailPartition service parameter values. The Cisco Messaging Interface with the higher service priority (the active Cisco Messaging Interface service) handles the SMDI responsibilities. If this Cisco Messaging Interface encounters problems, another one can take over.
From this doc;
http://www.cisco.com/en/US/products/sw/voicesw/ps556/products_administration_guide_chapter09186a008037e2f3.html#wp1024396
Hope this helps!
