The Tool Desk
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Who should own each part of an OTP message?
Separate decisions about the login experience from the technical work of sending a message. Assign accountable owners on the SaaS side, then document what each delivery provider does under the service arrangement.
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| Responsibility | Accountable owner | What it covers |
|---|---|---|
| OTP purpose and policy | SaaS product and security | Why a code is sent; its lifetime; resend limits; abuse controls; fallback behavior; and which login flows use it. |
| Template and sender policy | SaaS product and security | Approved wording, visible sender identity, supported languages and accessibility variants, and review of links, support details, and brand identifiers. |
| Provider and delivery setup | SaaS engineering or delivery operations | Provider-account access, verified sender assets, DNS records, credentials, routing, fallback logic, delivery telemetry, and incident escalation. |
| Message transport | SMS or email provider | Delivery under contract, channel-specific platform configuration, and technical support for applicable registration or setup processes. |
| Data-protection roles and terms | SaaS privacy or legal owner | Assessment of the actual data flows and purposes, determination of controller and processor roles, and appropriate processor terms where applicable. |
Keep templates versioned and require review before changing the code instructions, sender identity, links, or support wording. A provider’s configuration interface may be where a message is entered or a sender is registered; it should not be the only record of the SaaS’s approved content and login rules.
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How do SMS and email differ operationally?
The main established differences are in sender setup and administration—not proven differences in login speed, completion, fraud, or price. The available official sources do not provide comparable performance figures for SMS versus email OTP. Use your own delivery, completion, recovery, and abuse telemetry to assess those outcomes.
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| Area | SMS OTP | Email OTP |
|---|---|---|
| Sender identity and control | The SaaS should set the sender-identity policy and own the business details submitted for applicable registration. Provider and carrier processes vary. | The SaaS should control the visible From identity and the domain used for transactional mail. |
| Registration burden | Depends on sending method, provider, carrier process, and destination. For AWS-documented US 10DLC registration, the sequence is brand registration followed by campaign registration; brand vetting is optional and described as a way to increase messaging capacity. AWS registration guidance. | Requires sender-domain authentication setup and maintenance with the relevant mail provider and DNS owner. European Commission email standards overview. |
| Country-specific setup | Check the chosen provider’s current rules for each destination country. Brevo, for example, says its platform requires sender registration for each destination country for transactional as well as marketing SMS; that is Brevo’s policy, not a universal rule for the EU. Brevo sender-registration guidance. | Domain authentication is configured through DNS and the mail provider; keep the SaaS accountable for the domain and visible identity. |
| Delivery and fallback observability | Instrument provider status, delivery outcomes, retries, and fallback decisions in the SaaS’s own systems. | Instrument sending and delivery outcomes, recovery paths, and fallback decisions in the SaaS’s own systems. |
| Recovery and abuse controls | The SaaS owns resend limits, code expiry, abuse safeguards, and fallback behavior. | The SaaS owns resend limits, code expiry, abuse safeguards, and fallback behavior. |
What must the SaaS decide for US SMS?
If using a US 10DLC route through AWS End User Messaging SMS, AWS documents a process that starts with brand registration and then campaign registration. Optional brand vetting is described as a way to increase messaging capacity. This makes the SaaS’s business identity and campaign information an operational responsibility that needs a clear internal owner, even when a provider supports the submission.
Do not assume that the AWS sequence applies unchanged to every provider or sending method. Confirm the selected provider’s current US requirements before launch, and keep the SaaS owner responsible for the accuracy of submitted identity and use-case details.
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What must the SaaS decide for EU SMS?
There is no single blanket EU sender-registration rule established here. Requirements can differ by country and provider. Brevo’s country-by-country registration policy is a useful example of a platform requirement, but it does not show that every provider or EU jurisdiction imposes the same requirement.
Before enabling a destination, check the chosen provider’s current country guidance and applicable local rules. Make that review part of destination launch and change management rather than assuming that approval in one country covers all others.
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What does email OTP domain authentication involve?
Keep the sender identity and transactional-mail domain under SaaS control. Coordinate with the email provider and the DNS owner to configure and maintain three complementary mechanisms:
- SPF identifies the sending hosts authorized by a domain.
- DKIM uses a digital signature to verify the sending domain’s message and detect alteration in transit.
- DMARC tells receiving systems how to handle mail that appears to come from the domain but fails SPF or DKIM checks, and can provide reporting.
The FTC recommends SPF, DKIM, and DMARC for businesses using their own domain email and explains that DMARC aligns the authentication identity with the visible From address. See the FTC cybersecurity guidance for small businesses. Provider tooling can help configure these records, but the SaaS should retain ownership of its domain, sender policy, and operational review.
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How should GDPR roles be assigned to OTP vendors?
For EU data-protection purposes, the role depends on what each party actually does. GDPR defines a controller as the person or body that, alone or jointly, determines the purposes and means of personal-data processing; a processor handles data on a controller’s behalf. The contract label alone does not settle the question.
Assess the OTP data flow and the parties’ real decisions, then document the roles and instructions. Where a vendor is acting as a processor, GDPR Article 28 requires an appropriate binding arrangement and documented instructions, subject to the regulation’s stated legal exception. Review the GDPR text with the actual vendor relationship in view.
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Does payment SCA dictate OTP for every SaaS login?
No. Commission Delegated Regulation (EU) 2018/389 sets technical standards for strong customer authentication in the payment-services context; it should not be treated as a rule selecting SMS or email for every ordinary SaaS sign-in. Keep payment authentication flows distinct from routine account login, and obtain legal review for regulated payment use cases. See Commission Delegated Regulation (EU) 2018/389.
Quick Recap
What should an ownership policy include?
- Name a SaaS product or security owner for OTP purpose, approved text, sender policy, supported locales, expiry, resend limits, abuse controls, and fallback behavior.
- Name an engineering or delivery-operations owner for provider access, sender assets, DNS, credentials, routing, telemetry, and incidents.
- Version templates and record who approved each change, especially changes to links, support wording, and brand identifiers.
- For each SMS destination, verify the chosen provider’s current country-specific requirements; for US 10DLC, assign an owner for the required provider workflow.
- For email, assign responsibility for SPF, DKIM, and DMARC records alongside control of the visible sender identity and sending domain.
- Have privacy or legal review actual vendor data flows and document controller/processor roles and terms where applicable.
- Measure delivery, login completion, recovery, and abuse in your own system before making channel-performance comparisons.
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