lity to reply to and forward voicemail and e-mail; the ability to add other attachments; the ability send voicemail and e-mail via distribution lists; telephone user interface-based retrieval of voicemail or e-mail; callout of system voicemail delivery; voicemail notification options; scheduled delivery of voicemails; the ability to dial back from the inbox interfaces; and mobility features. Early marketing efforts for IPT systems focused on a variety of cost-saving and productivity benefits, with little emphasis on the advantages of a more flexible sys- tem design. However, it is becoming evident that these two benefits are best real- ized by taking advantage of a third aspect of IP PBXs: their inherent ability to provide a more modular and survivable configuration compared with traditional circuit-switched TDM PBXs. Customers with multiple premises can configure an IP PBX to operate seamlessly across two or more locations at a lower cost and with greater performance capabilities than a network of standalone systems would offer. One of the major factors in the accelerated migration to the new IP-based plat- forms is their ability to replace multiple standalone systems, such as key telephone systems, hybrids, or standard PBXs, with a single IP PBX system that uses surviv- able remote equipment to create a dispersed architecture. The ability to leverage an existing data network infrastructure for both call control signaling and voice com- munications transmission is a relatively recent enhancement to IPT. However, because IPT architectures are based on LAN/WAN connections, the enterprise must ensure that backup systems are in place in the event of a loss of LAN/WAN connectivity. Several IPT design options are available to customers who favor a single- system approach to serve multiple premises. These options range from the simplicity of remote, standalone IP telephones to standalone servers coupled with fully provi- sioned distributed port carrier cabinets that function as media gateways between traditional statio