How to transfer an external SIP call directly to a Teams user's voicemail?
Hi, I am working on an external SIP-based reception platform that connects to Microsoft Teams through Direct Routing. My requirement is to transfer an external call directly to a Teams user's voicemail without ringing the user's Teams devices. The current flow is: External Call → Reception Platform → SIP/Direct Routing → Microsoft Teams A normal SIP transfer to the Teams user's SIP address rings the user. I need the call to go directly to their Teams voicemail. I have been investigating SIP REFER/INVITE and found references to using: sip:email address removed for privacy reasons;opaque=app:voicemail I also found information about a User-to-User SIP header, but I am not sure which approach is officially supported by Microsoft Teams Direct Routing. I have tried the opaque=app:voicemail approach, but I have not been able to get the call to reliably go directly to voicemail. Could someone please clarify: What is the officially supported way to transfer an external SIP call directly to a Teams user's voicemail? Is opaque=app:voicemail supported with Direct Routing/SBC? Is there a specific SIP header or URI parameter required? Should the SBC modify the REFER or the subsequent INVITE? Any Microsoft documentation or example SIP messages would be very helpful. Thanks!