STIR/SHAKEN attestation, explained in plain English

STIR/SHAKEN isn't a spam filter. It's a signing protocol. When a call leaves an originating carrier, that carrier cryptographically signs a claim about the calling number — whether it owns the number (A), whether it knows the customer (B), or whether it's just passing the call through (C).

Terminating carriers then decide what to do with that signature. Most US carriers downgrade or mark any call that isn't A-attested. A lot of outbound teams blame their dialer for "Spam Likely" when the real issue is that their upstream is signing B or C because they never verified number ownership.

The fix is operational, not technical: get your numbers properly provisioned, complete the RespOrg / TN verification paperwork, and work with a carrier that signs A-level attestations on verified TNs by default. VOIPONE's provisioning portal marks each DID with its current attestation level and the next action needed to upgrade it.

Attestation alone won't save you from being flagged as spam — reputation still matters. But getting to consistent A-level attestation is the price of admission in 2026.