Hi, I'd like to make some actions in the ser.cfg file when the SIP message matches the REGISTER action, but only when it corresponds to the unregistration of the user. How can I distinguish both cases?. Is there any command I can include in my ser.cfg file?. I know that unregistration REGISTER messages include a header field: "Expires: 0" but I don't know how to find this string in the message. There's no $SIP_HF_EXPIRES. Thanks