This means many things depending on who you are talking to. True Unified Messaging will allow your telephone system voice mail messages as well as faxes be forwarded to your email so that you can view faxes and listen to your messages from one place like your computer or smart phone: If this is important than an IP system or an IP Hosted system is important.
Is it important to interface your smart phone with your phone system. With true Mobility your smart phone can have all of the advantages of your desktop phone. Make outgoing calls with your office phone number showing in the caller ID. Place calls on hold, transfer and call park should all be built into your mobility solution. If this is important only a few IP systems and even fewer IP Hosted solutions have full feature mobility.
SIP trunking is the latest method of line delivery, and having burstable SIP trunking allows you to have as many lines as needed on demand without paying for these resources if not needed. Make sure your IP system is native SIP which will allow you to add SIP trunks without paying for licensing.
Do I have to have line appearances in my new system? Line appearances show what analog phone line that you are on, and if you put a call on hold at your phone on a specific line number, you should be able to walk to another phone in the office and see that blinking line number and answer it. More companies find that this is not important and desire the Call Park function. Parking a call allows you to press a button on your phone to park a call and by knowing the parking spot number, anyone can go to any telephone in their system, enter the parking spot number, and retrieve the call. Most hosted systems today cannot allow for line appearances and rely entirely on the call park function
Many larger companies have multiple locations and the intelligent telephony systems of today will network these multiple locations, giving the functionality of all being under one main building. Calls from extension to extension, transferring calls, picking up parked calls and much more are all available between the multiple offices. Even having the ability to see if someone from another office is on the phone or away from their desk is a basic feature found in Presence of the system.
Do I want multiple offices assisting in call flow? By having multiple offices on one system, you have to ability to "follow the sun" in service call response. Offices on the East Coast or Europe can handle service calls early in the day and as the day continues, this functionality can be performed by West Coast offices.
Many of the new systems today allow larger companies to choose any of the three or even mix between the three in multiple offices and yet keep all of the same functionality no matter what platform is chosen.
Native sip today allows far greater capabilities both today and moving into the future. If your new system is NOT Native Sip, then you most likely will be held hostage to limited capabilities created by the manufacturer. Since Native Sip allows for integration with many technologies in an OPEN PLATFORM, Native Sip systems can take advantage of other Native Sip creations in implementing greater telephony functionality each other's systems.