Make sure tandem CO connection, trunk access allowed, and through dialing checked in the COS of the VM ports. I have only ever used this on a PRI and SIP trunks where all calls were either going through the AA and then being xferred to the station that was set to call forward external. I have also gotten it to work for DID calls. I have not gotten it to work with analog trunks, but it's a bad idea to use analog trunks to call forward external.

If you are going to do this for more than a user or two, make sure that you have enough available trunks on the system as every call will now take two trunks.

Thanks,
Daniel