We have a fairly large install of 3CX wint Polycom VVX-410 phones. We can't really get support for it because the phones we have are using non-standard provisioning templates and the phone we're having the most problems with is the phone 99% of all calls are filtered through (the main receptionist). What happens is that an external call comes in on the main number, the caller asks to be transferred to the individual's voicemail, the receptionists transfers the call immediately with "*4 nnn". The call then drops. I've collected pcaps on this numerous times and while analyzing them what I've found is that the call drops when this happens: SIP/2.0 100 Trying NOTIFY sip:firstname.lastname@example.org SIP/2.0 Via: SIP/2.0/UDP 10.10.0.21:5060;branch=z9hG4bK-524287-1---032249177f473242;rport Max-Forwards: 70 Contact: To: "Username" ;tag=3A83B12E-5E1E9C87 From: "RG - Main Numberrimary DID:XXX" <sip:+email@example.com:5060;nf=e>; tag=ae59e637 Call-ID: iNZxXNn_H907j4JGkijm0A.. CSeq: 3 NOTIFY Content-Type: message/sipfrag User-Agent: 3CXPhoneSystem 15.5.6354.2 (6180) Subscription-State: terminated;reason=noresource Event: refer;id=2 Content-Length: 25 SIP/2.0 404 Not Found I've been pulling my hair out trying to figure out why these transfers simply drop. Anyone have any insight?