On inbound Direct Routing calls Microsoft uses the From header, which must carry a + prefixed number, to check the callee's blocked-number list and to look up the caller's name.
Checked 2026-10-02
- Vendor
- Microsoft
- Product
- Teams Phone Direct Routing
- Subsystem
- SIP proxy
- Deployment
- multi-tenant
- Region
- not restricted
- Release range
- current as of 2026-10-02
- Checked
- 2026-10-02
Sources
- Teams Phone System Direct Routing: SIP protocol — Microsoft · tier 2 current vendor documentation · Processing the incoming request > From Header
Cite this note
APA
WarmTransfer. (2026, October 2). SIP identity headers: P-Asserted-Identity and Diversion and History-Info: source note sip-identity-headers-teams-from-lookups. WarmTransfer. https://warmtransfer.net/knowledge/claims/sip-identity-headers-teams-from-lookups
BibTeX
@misc{warmtransfer-claim-sip-identity-headers-teams-from-lookups,
title = {SIP identity headers: P-Asserted-Identity and Diversion and History-Info: source note sip-identity-headers-teams-from-lookups},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/sip-identity-headers-teams-from-lookups},
note = {Source note sip-identity-headers-teams-from-lookups, checked 2026-10-02}
}