Yes. If you are using your SIP device behind a firewall, or NAT device, you may need to use the DrayTEL proxy instead of accessing DrayTEL in direct mode. To do this, set your outgoing proxy to nat.draytel.org:5065 (the exact method will depend on your VoIP/SIP device. Do not use the proxy if your VoIP device is on a public IP address. DrayTEL does not operate a STUN server (and equivalent method).