Trunk to Trunk Routing

[Wendelspanswick]

We have a Mitel 3300 which has DASS trunks, SIP trunks and a SIP trunk link to a 3CX system, we are trying to route out calls from the 3CX through the 3300 and onto either the DASS or SIP trunks.
Internal calls between the two systems works perfectly.
The Mitel has a Digits Dialed route for 7 that sends calls out on the DASS, this works.
We have set up an outbound route on the 3CX with no digits absorbed so that dialing 7 sends out a call on the SIP link between the two systems, the call hits the Mitel but gets rejected with:
MitelIPaddress replied: 403 Forbidden; warning: 29H Access Barred
I have allowed Public Trunk to Public Trunk Connection Allowed for all trunks.
Am I missing a step?

[sarond]

My first guess is going to be COR.

Check the COR of the 3CX trunks is allowed to make an outbound call.

[Wendelspanswick]

Spot on, that worked!
Thank you, I gave the 3CX SIP trunk the same COR as the DASS trunk as I couldn't find where in the programming you changed the attributes for the COR groups?