# OTP Delivery Optimization Checklist - Canonical URL: https://www.broadnet.me/guides/otp-delivery-optimization-checklist - Language: en - Publisher: BroadNet (https://www.broadnet.me) - Markdown version of the page above, generated from the rendered page. OTP & Verify Free checklist A practical checklist to improve one-time-password delivery: channel fallback, sender-ID and templates, latency and retries, message design, and protection against AIT / SMS pumping. 24 checkpoints 2 min read Updated July 14, 2026 Email me the PDF For product and growth engineers who own signup, login, and transaction verification. What's inside 1. 01Channel strategy & fallback 2. 02Sender ID, templates & routing 3. 03Latency & retries 4. 04Message & code design 5. 05Fraud & AIT (artificially inflated traffic) protection [Browse all guides](https://www.broadnet.me/guides) The short version One-time passwords are the highest-stakes messages most businesses send: a late or undelivered OTP is a failed login, an abandoned signup, or a lost transaction. Optimising OTP delivery means treating it as a distinct traffic class — short validity, low latency, the right route and sender ID per market, sensible fallback, and hard controls against artificially inflated traffic (AIT) that quietly drains your budget. Work through each group and instrument what you can measure. The checklist ## Work through it, tick as you go. Diagram The OTP journey, with channel fallback 1. User requests a code Sign-in, payment or sign-up 2. Your app calls the verify API One request per code 3. BroadNet delivers the code On the best available channel Fallback if undelivered SMS WhatsApp Voice 4. User enters the code Checked against the issued code 5. Verified Access granted 01 ### Channel strategy & fallback - Define a channel waterfall per market (e.g. SMS → WhatsApp/RCS → voice call). Fallback should be time-boxed: if channel one isn't confirmed in N seconds, escalate. - Prefer app-native verification where available (silent/OTP autofill, app-based push) to cut SMS dependency. - Use voice OTP as a fallback in markets with poor SMS deliverability or for accessibility. - Avoid sending the same OTP across two channels simultaneously — it doubles cost and AIT exposure. 02 ### Sender ID, templates & routing - Register sender IDs where the market requires it; unregistered IDs are frequently dropped. Sender-ID pre-registration is mandatory in a growing number of markets. - Use a dedicated, low-latency OTP route separate from marketing traffic. Never share a route between transactional OTP and promotional bulk. - Keep template content minimal, branded, and consistent to pass content filters. - Support autofill formats (e.g. the origin-bound one-time-code convention on the last line) to speed entry. - Set a short validity_period so a delayed OTP expires instead of arriving stale. 03 ### Latency & retries - Measure end-to-end latency to handset (submit → DLR), not just submit-accept latency. - Set a resend cooldown and cap resends per user per window. Uncapped resends are the primary attack surface for SMS pumping. - Trigger fallback on missing DLR within your latency budget, not only on explicit failure. - Deduplicate: one logical verification = one code, even across retries, to avoid confusing the user. - Instrument delivery rate, median/p95 latency, and conversion (code entered) per market. 04 ### Message & code design - Use 6-digit numeric codes as a default; longer only where policy requires. - Bind the code to the session/device and expire it server-side after first use or timeout. - Localise the message body while keeping the code and brand token stable. - Never include the code in a clickable link that could be phished; keep it copy/type only. 05 ### Fraud & AIT (artificially inflated traffic) protection AIT / SMS pumping fraud generates real OTP requests to numbers the fraudster controls, inflating your bill with no legitimate user. This is the highest-ROI section for most senders. - Rate-limit OTP requests per phone number, per IP, and per device fingerprint. - Add friction (CAPTCHA / challenge) when velocity spikes from a source. - Block or throttle high-risk destination ranges and known-bad number prefixes. Sudden traffic to an unusual country range is the classic AIT signature. - Monitor conversion rate per destination — pumped traffic shows requests with near-zero code entry. - Use number-intelligence / HLR lookup to reject invalid or high-risk numbers before sending. - Work with a provider that offers AIT detection and will act on suspicious patterns. References - [RFC 6238 · TOTP](https://datatracker.ietf.org/doc/html/rfc6238) - [GSMA · fraud & security (FS series)](https://www.gsma.com/solutions-and-impact/technologies/security/) Standards and regulator references cited in this guide. BroadNet is a GSMA Associate Member and MEF member operating carrier-grade messaging since 2003. Related - [OTP / Verify product](https://www.broadnet.me/products/otp) - [What is an OTP?](https://www.broadnet.me/answers/what-is-otp) - [SMS segment calculator (free tool)](https://www.broadnet.me/tools/sms-segment-calculator) - [Telecom fraud prevention checklist](https://www.broadnet.me/guides/telecom-fraud-prevention-checklist) - [Coverage & operators](https://www.broadnet.me/coverage) Keep a copy ## Want this as a shareable PDF? Send it to your inbox to circulate with your team — no spam, one email. Email me the PDF Get the PDF ## Email me the OTP Delivery Optimization Checklist. We'll send a clean, printable PDF of this checklist to your inbox so you can circulate it with your team or keep it for your RFP. A messaging engineer will follow up only if you ask — no sales spam. - Printable, one-page-per-section PDF - Everything on this page, formatted to share - Optional: a call with a BroadNet engineer Prefer not to share your email? Use Print / save as PDF above — the full checklist is on this page. Direct line · reply within one business day ## Send me the OTP Delivery Optimization Checklist Tell us where to send it. We'll email the PDF and only follow up if you ask. 1. 1 Who 2. 2 Need 3. 3 Context