Which protocol is often associated with the delivery of Unified Messaging services?

Unified Messaging (UM) services combine various communication modes, such as voicemail, email, and fax, into a single interface, enhancing the user experience and centralizing communication management. Exchange ActiveSync is the correct choice because it is designed to synchronize mobile devices with Microsoft Exchange Server and includes support for email, calendar, contacts, and tasks, which are integral to Unified Messaging.

This protocol allows for real-time syncing and offers capabilities necessary for delivering these integrated services seamlessly across different platforms. It enables users to access and manage their messaging services on the go, making it particularly suited for Unified Messaging solutions.

In contrast, the other protocols mentioned, while essential for different functionalities, do not directly support Unified Messaging in the same comprehensive way. IMAP and POP3 are primarily for retrieving emails and do not encompass the broader features offered by Unified Messaging. SMTP, on the other hand, is used for sending email but does not inherently manage the integration of voice, fax, and other forms of communication in a unified manner. Therefore, Exchange ActiveSync stands out as the protocol that effectively supports and delivers Unified Messaging services.