Hi, I made an investigation on possibilities of handling 423 response in PJSUA and found out that there is no chance. The only info I can get is that last response to REGISTER was 423, but nothing more. The only place where I could browse response headers is in PJSUA's regc_cb (callback passed in pjsip_regc_create). Is anyone interested in solving the issue? In similar previous thread two ways to go were proposed: 1) introducing on_reg_state2 PJSUA callback with more information, 2) handle 423 in the same way as 401, 407 responses. If you decide to make a patch, could you tell me, whether can I expect it in 1.0.x branch as well? Greetings and thanks - Vali