Is end-to-end encryption available for all calls in GCC High Teams, including PSTN calls to external numbers?

End-to-end encryption (E2EE) is available for Teams-to-Teams calls within the GCC High environment, but it is not available for PSTN calls to external phone numbers. This is a protocol-level limitation, not a GCC High-specific restriction.

When two GCC High Teams users call each other, the call can be encrypted end-to-end so that only the two participants can access the audio. When a call routes to an external phone number through the PSTN, the encryption chain breaks at the SBC gateway where the call transitions from the Teams digital environment to the traditional telephone network. The PSTN infrastructure does not support E2EE. Within the GCC High boundary, PSTN calls are still protected by TLS encryption on the signaling path and SRTP encryption on the media path between the Teams client and the SBC. The call travels through compliant, U.S.-only infrastructure up to the PSTN handoff point. Organizations that need fully encrypted voice communications for sensitive discussions should use Teams-to-Teams calls within the GCC High tenant rather than PSTN calls to external numbers.