require a contact header
I've been reading about whitelist and am wondering if it can do what I need it to do. Basically, I want it to check to see if there are particular headers in a message and if not, reject the message. For example, I want a contact header in every registration and if it is not there, I want the SD to reject it. Is this possible with a whitelist? If not, what is better to use? An HMR?