[HELP] Disable call forwarding for one call


I’d like to tell my Snom 320/360 phones to disable the call forwarding feature for certain calls. Incoming calls from PSTN should be forwarded als configured in the phone, but internal calls from other SIP phones should ring the phone. Is there for example a SIP header field which tells the phones to disable call forwarding?
The feature “forward external calls” is present in many PBXes, I wonder if it is realised in *.


I don’t know if this can be done through SIP headers and the like, but you could set it up in the dialplan, as in this example: voip-info.org/wiki-Asterisk+call+forwarding