atcomsystems.ca/forum Forums TDM Business Telephone Systems Mitel Telephones & Systems callforwarding an ext.to an external phone number

As mitelman said you must also check the interconect restrictions table and see if isn't an R (restriction) between the interconect number(s) of the two trunk (the incoming trunk and the outgoing trunk). And also check Public Network to Public Network Connection Allowed option enabled in the COS of the trunks and station.