I have a small Asterisk server setup that works correctly with the aastra 9143 phones that are attached to the same network. I setup a VPN tunnel from another location so I can use a remote phone but I cannot seem to get any outbound calls to work correctly from this phone. The phone will sip register and it can successfully receive calls from the PBX from PTSN or Extensions. It simply cannot make any outbound calls.
Is the network the remote phone on in the list of allowed local networks in SIP settings?