I am not using a normal soft phone. I am using an automated voice alarm dialing service provided by Ignition (inductiveautomation.com). It uses SIP and is normally set up to port 5060. The software works well on an ATCOM IP-01 as well as a Linksys SPA3102. I am not using a provider on the internet, and I want all of my calls to go out over the PSTN (AT&T). I am not interested in incoming calls at this time.