Ok, so I setup a 3CX 3U appliance with 20 Cisco 504G phones, a couple of Snom M3's and have a 6 SIP trunk line through Broadvox through a Cisco RV082 router. Everything configured and setup perfect at office network. Move all equipment to customer site. Setup everything, change external IP on router and in 3CX fields where needed to match customer's static IP config and we can receive calls through VOIP Provider, make internal calls, but cannot call out. As soon as you try, phone read "server internal error". Server Activity Log shows (xxx'd out phone number for security): 21:07:11.645 [CM503016]: Call(4): Attempt to reach <sip:email@example.com> failed. Reason: Not Acceptable HereReason Unknown 21:07:11.644 [CM503003]: Call(4): Call to sip:firstname.lastname@example.org:5060 has failed; Cause: 400 Bad Request; from IP:188.8.131.52:5060 What gives?