SIPAddHeader( ) Adds a SIP header to the outbound call
SIPAddHeader(Header: Content)
Adds a header to a SIP call placed with the Dial( ) application. A nonstandard SIP header should begin with X-, such as X-Asterisk-Accountcode:. Use this application with careadding the wrong headers may cause any number of problems.
Always returns 0.
exten => 123,1,SIPAddHeader(X-Asterisk-Testing: Just testing!)
exten => 123,2,Dial(SIP/123)