Which protocol is transmitted by Cisco Unified Personal Communicator and connects to Cisco Unity Connection to retrieve and manage a list of voice messages for the user?

TCP is a transport-layer protocol that carries application data but is not itself the protocol used to retrieve and manage messages.

UDP is a connectionless transport-layer protocol and is not used for reliable message retrieval or mailbox management operations.

HTTP is used for web-based communication and REST APIs but is not the protocol Cisco Unified Personal Communicator uses to interface with Unity Connection for voicemail access.

IMAP (Internet Message Access Protocol) is the application-layer protocol used by Cisco Unified Personal Communicator to authenticate to and communicate with Cisco Unity Connection's IMAP server interface. IMAP allows the client to list, read, move, and delete voice messages stored on Unity Connection without downloading all messages locally, which is essential for managing a voicemail inbox through a unified client.