Hi, During proxy authentication, I got "mandatory IE missing" error in the response as shown below. How this error can be resolved? recv 585 bytes from udp/[209.82.10.250]:1898 at 15:31:39.933782:    ------------------------------------------------------------------------    INVITE sip:9999@209.82.10.235 SIP/2.0    Via: SIP/2.0/UDP 209.82.10.250:1091    From: HC-Desktop <sip:1002@209.82.10.235>;tag=55409708    To: sip:9999@209.82.10.235    Contact: sip:1002@209.82.10.250:1091    Call-ID: 8e6df5d2-0367-43d9-bda8-f51a94033473@192.168.10.31    CSeq: 421988828 INVITE    Content-Length: 187    Content-Type: application/sdp    User-Agent: HelpCaster SoftPHONE    Supported: com.hearme.mux      v=0    o=HelpCaster 153553387 153553387 IN IP4 192.168.10.31    s=HelpCaster    c=IN IP4 209.82.10.250    t=0 0    m=audio 8002 RTP/AVP 0 4 101    a=rtpmap:101 telephone-event/8000    a=fmtp:101 0-15    ------------------------------------------------------------------------ send 294 bytes to udp/[209.82.10.250]:1091 at 15:31:39.934100:    ------------------------------------------------------------------------    SIP/2.0 100 Trying    Via: SIP/2.0/UDP 209.82.10.250:1091    From: HC-Desktop <sip:1002@209.82.10.235>;tag=55409708    To: sip:9999@209.82.10.235    Call-ID: 8e6df5d2-0367-43d9-bda8-f51a94033473@192.168.10.31    CSeq: 421988828 INVITE    User-Agent: FreeSWITCH-mod_sofia/1.0.2-hacked    Content-Length: 0      ------------------------------------------------------------------------ send 746 bytes to udp/[209.82.10.250]:1091 at 15:31:39.938913:    ------------------------------------------------------------------------    SIP/2.0 407 Proxy Authentication Required    Via: SIP/2.0/UDP 209.82.10.250:1091    From: HC-Desktop <sip:1002@209.82.10.235>;tag=55409708    To: <sip:9999@209.82.10.235>;tag=K83mZmZH8g3Hr    Call-ID: 8e6df5d2-0367-43d9-bda8-f51a94033473@192.168.10.31    CSeq: 421988828 INVITE    User-Agent: FreeSWITCH-mod_sofia/1.0.2-hacked    Accept: application/sdp    Allow: INVITE, ACK, BYE, CANCEL, OPTIONS, PRACK, MESSAGE, SUBSCRIBE, NOTIFY, REFER, UPDATE, REGISTER, INFO, PUBLISH    Supported: timer, precondition, path, replaces    Allow-Events: talk, presence, dialog, call-info, sla, include-session-description, presence.winfo, message-summary, refer    Proxy-Authenticate: Digest realm="209.82.10.235", nonce="248a2800-7fd2-4a6f-8082-5d1731f3cf54"    Content-Length: 0      ------------------------------------------------------------------------ recv 280 bytes from udp/[209.82.10.250]:1898 at 15:31:39.949517:    ------------------------------------------------------------------------    ACK sip:9999@209.82.10.235 SIP/2.0    Via: SIP/2.0/UDP 209.82.10.250:1091    From: HC-Desktop <sip:1002@209.82.10.235>;tag=55409708    To: <sip:9999@209.82.10.235>;tag=K83mZmZH8g3Hr    Call-ID: 8e6df5d2-0367-43d9-bda8-f51a94033473@192.168.10.31    CSeq: 421988828 ACK    Content-Length: 0      ------------------------------------------------------------------------ recv 584 bytes from udp/[209.82.10.250]:1898 at 15:31:39.953137:    ------------------------------------------------------------------------    INVITE sip:9999@209.82.10.235 SIP/2.0    Via: SIP/2.0/UDP 209.82.10.250:1091    From: HC-Desktop <sip:1002@209.82.10.235>;tag=55409708    To: sip:9999@209.82.10.235    Contact: sip:1002@209.82.10.250:1091    Call-ID: 8e6df5d2-0367-43d9-bda8-f51a94033473@192.168.10.31    CSeq: 421988829 INVITE    Content-Length: 187    Content-Type: application/sdp    User-Agent: HelpCaster SoftPHONE    Supported: com.hearme.mux    Proxy-Authorization:  Digest username="1002",realm="209.82.10.235",nonce="248a2800-7fd2-4a6f-8082-5d1731f3cf54",response=" d1614cd024acab0b794751285f5cb1fe",uri="sip:9999@209.82.10.235"      ------------------------------------------------------------------------ send 294 bytes to udp/[209.82.10.250]:1091 at 15:31:39.953336:    ------------------------------------------------------------------------    SIP/2.0 100 Trying    Via: SIP/2.0/UDP 209.82.10.250:1091    From: HC-Desktop <sip:1002@209.82.10.235>;tag=55409708    To: sip:9999@209.82.10.235    Call-ID: 8e6df5d2-0367-43d9-bda8-f51a94033473@192.168.10.31    CSeq: 421988829 INVITE    User-Agent: FreeSWITCH-mod_sofia/1.0.2-hacked    Content-Length: 0      ------------------------------------------------------------------------ send 696 bytes to udp/[209.82.10.250]:1091 at 15:31:39.956016:    ------------------------------------------------------------------------    SIP/2.0 480 Temporarily Unavailable    Via: SIP/2.0/UDP 209.82.10.250:1091    From: HC-Desktop <sip:1002@209.82.10.235>;tag=55409708    To: <sip:9999@209.82.10.235>;tag=mHXD1FgN5SS4K    Call-ID: 8e6df5d2-0367-43d9-bda8-f51a94033473@192.168.10.31    CSeq: 421988829 INVITE    User-Agent: FreeSWITCH-mod_sofia/1.0.2-hacked    Accept: application/sdp    Allow: INVITE, ACK, BYE, CANCEL, OPTIONS, PRACK, MESSAGE, SUBSCRIBE, NOTIFY, REFER, UPDATE, REGISTER, INFO, PUBLISH    Supported: timer, precondition, path, replaces    Allow-Events: talk, presence, dialog, call-info, sla, include-session-description, presence.winfo, message-summary, refer    Reason: Q.850;cause=96;text="MANDATORY_IE_MISSING"    Content-Length: 0      ------------------------------------------------------------------------ recv 280 bytes from udp/[209.82.10.250]:1898 at 15:31:39.964632:    ------------------------------------------------------------------------    ACK sip:9999@209.82.10.235 SIP/2.0    Via: SIP/2.0/UDP 209.82.10.250:1091    From: HC-Desktop <sip:1002@209.82.10.235>;tag=55409708    To: <sip:9999@209.82.10.235>;tag=mHXD1FgN5SS4K    Call-ID: 8e6df5d2-0367-43d9-bda8-f51a94033473@192.168.10.31    CSeq: 421988829 ACK    Content-Length: 0 Thanks!