Where OTPs are used
OTPs are most often used for two factor authentication (2FA) during login, for verifying a new phone number or email address, for authorising sensitive actions like password resets or large payments, and for guest checkout in e-commerce. The user receives a short code, types it back into the app, and the app confirms it matches what was sent.
Why OTPs work
An OTP needs secure random generation, single-use enforcement, a short expiry and strict attempt limits. Short numeric codes are guessable without rate limiting; interception and phishing remain risks.
Best practices for sending OTPs
Choose an appropriate code length and short expiry, bind the code to its user and purpose, and limit both generation and verification attempts. Do not expose codes in application logs. Your application owns code generation and verification.
How Senddio handles OTPs
Your application generates and validates the code, then uses Senddio to deliver it. For email set messageType to transactional. A tag is an analytics label, not an OTP priority or redaction switch. Senddio does not generate deterministic OTPs or guarantee a delivery deadline.