In the pjsua documentation http://www.pjsip.org/python/pjsua.htm#Buddy is written that optional headers can be added using hdr_list: send_pager(self, text, im_id=0, content_type='text/plain', hdr_list=None) Send instant message to remote buddy. Keyword arguments: text -- Instant message to be sent im_id -- Optional instant message ID to identify this instant message when delivery status callback is called. content_type -- MIME type identifying the instant message hdr_list -- Optional list of headers to be sent with the request. how ever I have not applied get to this work right. This is what I have tryed header_list = [] header_list.append("Subject=Test") header_list.append('Subject: Foo') header_list.append('Subject:, foo') ... some code buddy.send_pager(input,content_type='text/plain',hdr_list=header_list) and for result I get SIP MESSAGE with basic headers, but none of my optional headers except four ":" empty lines: MESSAGE sip:jari at mydomain.fi SIP/2.0. Via: SIP/2.0/UDP myip:5080;rport;branch=z9hG4bKPjRT8HRroNeYqMblLt8bxfSxI7rDfAUZR4. Max-Forwards: 70. From: <sip:jari@xxxxxxxxxxx>;tag=Rro.mo0pMTmkoiS8cAs74ELT4X.eve98. To: <sip:jari at mydomain.fi>. Call-ID: gA5YAVKuj-jRmVItXv.qE9VwM4dPpODt. CSeq: 63465 MESSAGE. Accept: text/plain, application/im-iscomposing+xml. Contact: <sip:jari at myip.fi:5080>. User-Agent: Jari's Python Script. : . : . : . : . Route: <sip:sip.mydomain.fi;lr>. Proxy-Authorization: Digest username="jari", realm="mydomain.fi", nonce="4b8e859d000005f04bf656f8fdd980b78d865ef27632a8e9", uri="sip:jari at mydomain.fi", response="a94938b0df8be6c407d95d93e5aa02d1", cnonce="0u45VvJKoydngfonnRbaapVgvuIhr.00", qop=auth, nc=00000001. Content-Type: text/plain. Content-Length: 12. . TEST MESSAGE ------------------------- What I am doing wrong or isit a bug? Cheers, Jari