I tried to configure 2 different SIP trunks from 2 different carriers. Both work outbound, but inbound calls are rejected with a 403 forbidden. One line is from a Mitel certified SIP carrier.

Any ideas?

Thanks
Shane

I struggle with this same issue a lot myself. The 403 means the SIP carrier is NOT getting a response [from the 5000] for the call 'invite'. Basically means the client's network is either blocking port 5060, OR their router is not 'SIP friendly' and you'll and up having to replace it with something else to get it to work.

We only use AccessLine with the 5000 and we run their PORT TESTER prior to ordering trunks to find out if client's LAN is SIP capable.

403 can be generated by a few things. 403 Forbidden usually means that either the usernmae/password used to authenticate is wrong, or the messaging is coming from an IP the carrier is not expecting.