Hi, my callers and my own test were getting about 50% "dead air" when we called the lines. It would answer and not do or say anything.. (I am using a digital receptionist) Its not a firewall nor VOIP provider issue because I am using a Windows 2003 as my 3cs serer with Routing and remote access and a direct IP on the internet with basic firewall on the same box, with all the correct ports open, (no middle man - other firewall). This set up is both notably faster than any other firewall I have EVER tested and secure, (6 or 7 years, not one problem, many servers) And I am using nexvortex and they are very good quality.. on top of that, all my tests were from inside of the network, thus bypassing the firewall and nexvortex VOIP provider, (dialing the digital receptionist directly). The things I have tried. "Allow Keep Alives", on -then off, (best is off for me.. By turning off, I now get only 1 out of 10 calls that go directly to "dead air") I have "Supports Replace" off "PBX delivers Audio" off "Supports Re-Invites" off I have it set to "require registration for" to "do not require" (not sure what that does, but it sounded less restrictive. LOL) Please do not respond with an insulting.. "Buy the commercial version and buy support" I truly think this is unwise for your sales. Why would I buy it if it does not work "out of the box"? On the other hand, I would love to get into this market. I have hundreds of business clients and many have asked about VOIP. I dred and hate Linux (just an anti geek stand, nothing to do with what can run for years without problems.. Kind a like my toaster.. It has been making toast for years.. No problems.. But then again, it only makes TOAST.. LOL) So, I like your product, look forward to making money setting it up, so my advice is just from what I have seen on this forumhttp://www.3cx.com/forums/voicemail-cutting-out-after-1-second-6381.html?view-post=31629#p31629.