I work for a VOIP company called AE40. One of our customer thinks of buying Yeastar PBX and using our software that includes a SIP softphone.
1. Do you support third party SIP softphones?
2. Is it possible to make a call-transfer by sending a REFER message from our softphone to your PBX.
3. Is it possible to put a call on hold by sending SDP with "sendonly" from our softphone to your PBX?