Unified Messaging (UM) refers to the integration of different electronic messaging and communications media, such as e-mails, fax, or voicemail technologies, into a single interface, accessible from a variety of different devices. Before Exchange UM was introduced in Exchange 2007, IT administrators frequently managed an organization's voicemail/telephony network and e-mail systems/data networks as separate systems. E-mails and voicemails were located in distinct inboxes hosted by different servers and accessed through e-mail clients and telephones.

With the introduction of Exchange UM, administrators were finally able to combine e-mails, voicemails, and incoming fax into one universal inbox located on Exchange. This allows users to listen to their voicemail in their inbox, which can even be automatically transcribed into the e-mail, or by using any telephone and the Outlook Voice Access functionality.