We are trying to integrate our 3CX pbx with our own bespoke CRM system. We want to use the HTTP API makecall function so that we can automate the dialling of outbound calls by staff when clicking a call button in the CRM UI. The makecall HTTP API function is perfect but the calls don't work because 3CX seems to put the wrong values in the outbound SIP requests. When we make the call from a phone extension (102 in this case) it works perfectly, we can packet sniff the outgoing request as follows: SDP:Request: Invite sip:email@example.com:5060 .......... To: <sip:firstname.lastname@example.org:5060> .... From: "0292009272" <sip:email@example.com:5060> But when we initiate the call using the HTTP API, the api correctly calls the internal extension 102 first but then the subsequent outgoing SIP request is wrong: SDP:Request: Invite sip:firstname.lastname@example.org:5060 .......... To: <sip:email@example.com:5060> .... From: <sip:newsip.gradwell.net:5060> It doesn't seems to fill the from field with a valid SIP address. Also, the contact field seems to be incorrectly filled and is also missing the number@ part too. This manifests itself as an error back from our telephone provider: "error 407 Proxy Authentication Required". Perhaps this is understandable given that the SIP Request Invite hasn't properly stated the From and Contact fields. Other info: we are using v7.1 with Cassini web server on a dedicated WS03 SP1 x86 server in a data center with a public IP address. The extensions are in our office across the internet behind a NAT firewall. Please help - we need this functionality in order to justify using 3CX at all.