SMS sent from registered sender ID or recognized phone number

TCPA §227(b) and CTIA SMS Guidelines require SMS to be sent from a registered, stable sender identity — in the US, a 10DLC-registered long code, a carrier-approved short code, or a verified toll-free number. Sending commercial A2P SMS from unregistered long codes is no longer permitted under current US carrier requirements: unregistered traffic is filtered or blocked by AT&T, T-Mobile, and Verizon, meaning messages never arrive. Beyond deliverability, unregistered sending signals non-compliance to carriers, increasing the risk that the number is flagged and all future traffic from the same account is throttled.

Register your SMS sender identity with carriers before sending commercial A2P traffic. In Twilio Console, navigate to Messaging > Regulatory > A2P 10DLC.

US A2P Registration checklist:

1. Brand registration (one-time): company name, EIN, vertical
2. Campaign registration: use case, sample messages, opt-in description
3. Number association: link your long-code numbers to the approved campaign

Alternatives:
- Toll-Free Verification: faster (1–2 weeks), good for <100k msg/month
- Short Code: 8–12 weeks, highest throughput, best for >1k msg/day

If you use a Twilio messagingServiceSid (pool of numbers), all numbers in the pool must be 10DLC-registered. Verify registration status at Twilio Console > Messaging > Senders.