I had to explain this a couple times to friends so I figured I may as well post it. Visual voice mail is really audio IMAP. First you have you greeting. Its recorded and stored locally on the phone. Once the recording is made, it copies it to the AT&T server. Mine sounded great on the iPhone but when I tried calling my phone it had major distortions. I had recorded mine is low signal conditions. So, once you make you greeting you may want to place an actual call to the phone to make sure the server copy is clear. When someone calls they get the server copy of the greeting and leave a message. The message is kept on the voicemail server but a compressed copy is them sent, via Edge, to the phone. This is why a voicemail message seems to take a bit longer than normal to reach the phone. Since callers to you deal with the server, not you phone directly, they can listen to and leave messages when the phone is off or out of range (or in Airplane mode). Once the phone is on from an off state or back in tower range, it takes a bit for it to synchronize and get new messages. Since the messages are "copied" to the phone access to them is always there, even when you have no cell of edge coverage - this is a NICE feature. Also since the messages are still kept on the voicemail server (again, like IMAP e-mail) one can call their number form any phone and check, listen to messages and delete them. If you have no EDGE coverage, the iPhone will call into the voicemail server like any other phone has done before when checking for new messages.