hello the sofia stack responds to an outgoing invite with this message. the problem seems to be the following behavior from the endpoint (ip pbx) - 1st invite To: <sip:0123456789@sipserver> - server sends Proxy Authentication Required + nonce - pbx sends To: <sip:0123456789@sipserver>;tag=Sp1m3ayr748rH so the two sip dialoges do not match and the server respons with "Call Does Not Exist". is there a way to handle this (maybe broken) behavior from this sip client. possibly per user with an NDLB config option br -- Ing. Christian Löschenkohl Technische Leitung, Forschung & Entwicklung VoIP xpirio Telekommunikation & Service GmbH Lakeside B04 9020 Klagenfurt Austria T +43 (0) 5 77 11 - 1000 F +43 (0) 5 77 11 - 1002 E christian.loeschenkohl@xpirio.com