I'm finishing up my first 3CX installations and I'm down to my last two problems (I hope). I've configured a SIP Trunk provider (thinktel.ca) using the available template. The provider is registered and I can make incoming calls, but outgoing calls just go to dead air. Looks like the outgoing rule is working and routing the call properly to the SIP Trunk. The Server Activity Log shows: Code: 11:13:33.856 [CM503008]: Call(25): Call is terminated 11:13:30.899 Currently active calls - 1:  11:13:19.444 [CM503025]: Call(25): Calling VoIPline:2505551234@(Ln.10005@ThinkTel)@[Dev:sip:email@example.com:5060] So it appears that the call is going out to the SIP Trunk provider, but then nothing happens. And my cell phone never rings. The user hung up after 3 seconds. So if I'm understanding the log properly, 3CX thinks the calls been made successfully. So I tried it again, but this time waited longer before hanging up. About 10 seconds after the "Currently active calls" line, I got: Code: [CM503003]: Call(28): Call to sip:firstname.lastname@example.org:5060 has failed; Cause: 408 Request Timeout; internal Would the problem be with the SIP Trunk provider and not 3CX at this point? Authentication issue or something? FYI - I have a remote extension up and running in my home office and I can make/receive calls on it to/from other extensions at the Head Office (where 3CX is located). PS: Ran the firewall checker and everything is OK.