If your outbound calls are showing up as "Spam Likely" or "Scam Risk" on recipients' phones, STIR/SHAKEN is the framework explaining why — and how to fix it.
What STIR/SHAKEN is:
Secure Telephone Identity Revisited / Signature-based Handling of Asserted information using toKENs. (Yes, the acronym is forced.) It's a framework implemented in US and increasingly in other markets that cryptographically signs outbound calls to verify the caller's identity.
The attestation levels:
A (Full Attestation): The carrier knows the customer and their right to use the number being called from. This is the clean tier.
B (Partial Attestation): The carrier knows the customer but can't verify their right to that specific number.
C (Gateway Attestation): The call entered the network from an unknown source.
Why your calls get flagged:
Calls with B or C attestation are more likely to be marked as spam by receiving carriers. If you're using a VoIP provider that hasn't implemented STIR/SHAKEN, or you're routing through a gateway that strips the signature, your calls arrive without authentication.
How to fix it:
Use a VoIP provider that implements full STIR/SHAKEN attestation. Register your numbers with the provider in your name — don't use unregistered or ported numbers without verification. If using multiple carriers, ensure all legs of the call chain support the framework.
The technical fix takes hours. The business impact — significantly higher answer rates — is immediate.
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