Back in 1990, an X.400-like standard called AMIS (Audio Messaging Interchange Specification) appeared; these protocols enabled analog and digital voice messaging systems from different vendors to exchange messages. AMIS was more reminiscent of an email system than an interoperability protocol, and indeed its 1996 successor, VPIM (Voice Profile for Internet Messaging, also known as Voice Profile for Internet Mail), is based on SMTP/ MIME (Simple Message Transfer Protocol / Multipurpose Internet Mail Extensions).

At first glance, the combination of unified communications and contact centers should make for a potent brew, both in terms of streamlining operations and boosting the all-important "firstcall resolution" metric carefully monitored by all call/contact centers, that powerful indicator of both performance and customer satisfaction.

To take advantage of mobility and cost savings, enterprises are deploying dual-mode phones, which automatically switch between WiFi and cellular networks. By leveraging internal IP PBXs to handle calls using VoIP, rather than using the cellular network alone, enterprises can decrease costs, especially roaming charges, and provide improved mobility.