Twilio: SMS & Voice
SMS is the channel people actually read — which is exactly why it is regulated, filtered and easy to get wrong. Twilio supplies the rails; the integration supplies the judgment.
Texting customers is powerful and policed: sender registration (10DLC in the US, alphanumeric sender rules elsewhere), consent requirements, filtering that silently eats unregistered traffic, and international delivery that varies by country and carrier. The difference between Twilio "working" and Twilio working is entirely in that layer — the code is the easy part.
Typical builds: transactional SMS (orders, appointments, delivery windows), OTP verification with sensible resend and fallback logic (SMS OTP fails silently at the worst times; the integration handles it), and voice notifications where text will not do. Every build includes opt-out handling and delivery-event tracking, because a message firehose without delivery feedback is shouting into a closed door.
Honest boundary: marketing blasts are a different discipline — consent law, campaign registration and list hygiene belong to a messaging platform built for it, not to a website's integration layer. Transactional and operational messaging is the lane here, stated plainly.
What the engagement covers
- Transactional SMS wired to your events: orders, bookings, status changes, reminders
- OTP/verification flows with resend limits, expiry and a fallback path when SMS fails
- Sender registration and compliance plumbing (10DLC/alphanumeric) so messages actually deliver
- Opt-out handling (STOP/unsubscribe) done properly, not as an afterthought
- Delivery receipts tracked and surfaced — quiet filtering gets noticed, not assumed away
- Voice notifications where they fit (calls, IVR-lite flows) per the brief
Honest limits
What this is deliberately not.
Not this: Marketing blast campaigns and list buying — consent law and ESP-class platforms own that world
Not this: Guaranteed delivery to every handset — carriers filter; the integration sees it and routes around it
Not this: Two-factor replacing your auth system — the OTP flow integrates with it; the auth design is separate work
Not this: Spam-adjacent use of purchased numbers — declined, plainly
Questions · Twilio
Asked before building.
Almost always registration or filtering: US long codes now need 10DLC campaign registration, and unregistered or poorly-labeled traffic gets silently filtered by carriers. The diagnosis reads Twilio's delivery events (they tell you), fixes the registration or content pattern, and re-verifies. It is plumbing, not mystery.
For verification and transactional trust, yes — with honest fallbacks. SMS OTP fails at rates that surprise people (coverage, delay, SIM swaps), so a proper build pairs it with email fallback or authenticator apps for the critical paths. SMS-only 2FA on anything high-value is the wrong design, and the consult says so.
Two-way messaging is supported and sometimes genuinely useful (confirm/cancel by text), but it opens a compliance surface — opt-in language, auto-responses, and someone owning the inbox. Where replies matter, the flow is built for them; where they do not, one-way with a clean STOP path is the honest scope.
Twilio bills per message and per number — their pricing, transparent on their side. The integration cost here is scoped from the flows in the brief. Fixed quote, no invented numbers here.
Related: all integrations · the integrations stack page · the requirements template.
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