Why Business SMS Fail in Spain: Sender ID Registration, AWS Sandbox, Two-Way Numbers and DryRun

Technical report, October 27, 2026. An SMS platform accepts a request and returns a message ID, but the expected verification code never arrives. That result may involve an SMS sandbox, origination identity, country rules, carrier filtering or a delivery failure. Spain introduced a particularly significant change: since September 15, 2026, mobile operators must block SMS, MMS and RCS messages using unregistered alphanumeric sender aliases, or registered aliases sent through unauthorised origin providers.

What is an alphanumeric Sender ID?

An alphanumeric Sender ID displays a business name such as SHOPDEMO instead of a telephone number. It helps customers recognize the sender but also creates an impersonation risk. The Spanish CNMC National Alias Registry associates authorised names with their holders and permitted providers. Creating a sender ID resource inside AWS does not complete national registration, and registering an alias is not identical to registering a trademark.

Spain's rule and why it matters

The CNMC has confirmed that operators must block unregistered aliases and certain traffic sent through origin providers not enabled for the registered alias. This applies to Spanish recipients regardless of whether the application is hosted in Spain or abroad. Choosing a different cloud account or changing the business name shown to recipients does not avoid the rules. The goal is preventing brand spoofing and fraudulent messages.

Understanding the AWS SMS sandbox

In the AWS End User Messaging SMS sandbox, real sending is limited to verified destination numbers. A phone listed as PENDING has not completed verification; requesting a code and receiving an API message identifier does not prove delivery. AWS account tier, spending limits, destination restrictions, origination identity and carrier filters must be assessed separately.

Diagnosing a verification code that does not arrive

Check E.164 formatting, AWS Region, account tier, eligible origination resources, country settings, applicable quota limits and delivery events. Do not assert that an unregistered business alias caused a verification-code failure without evidence that the verification code actually used that alias. Preserve the message identifier and timestamp for a private provider support request; avoid repeated sends without a reason.

aws pinpoint-sms-voice-v2 describe-account-attributes --region eu-west-1
aws pinpoint-sms-voice-v2 describe-protect-configurations --region eu-west-1
aws pinpoint-sms-voice-v2 describe-verified-destination-numbers --region eu-west-1

These calls read configuration; they do not deliver SMS. An empty protection-configuration result does not rule out sandbox or carrier restrictions.

Registering a Spain business sender alias

1. Choose a legitimate, recognisable alias that meets AWS and CNMC requirements, including sender-length and capitalization rules.
2. Collect company identification and evidence of a lawful relationship to the name, such as trademark, legal business name or domain rights where accepted.
3. Start the Spain sender registration in AWS and obtain the origin-provider details needed for the national process.
4. Complete the CNMC process using an accepted digital certificate or a formally authorised representative.
5. Confirm any verification requests and submit matching holder, use-case, provider and sample-message details to AWS.
6. Wait until registration is Complete, then test delivery with a consenting recipient.

AWS publishes a roughly 28-day estimate for Spanish alphanumeric sender ID registration, not a guaranteed turnaround. A cloud account registered in another country remains subject to the destination country's communications requirements.

Dedicated numbers: a different origination model

A dedicated long code is a telephone-number origination identity assigned to an account, rather than an alphanumeric brand label. It is not subject to the Spanish alias registration requirement, but may require its own provisioning and messaging authorizations. It can potentially receive replies if two-way SMS capability is enabled.

The AWS country capability table lists Spain as supporting long codes and two-way SMS. This does not guarantee that any specific number ordered for Spain is configured for both directions. Confirm the capability and permitted use with AWS before paying.

Dedicated Spanish number: estimated pricing

AWS pricing lists a Spanish long code at US$20 per month and US$0 setup, plus message traffic, applicable taxes and other services. The commercial table suggests approximately one week for provisioning, while the registration-time guide lists fifteen days; treat both as estimates. Spain's provisioning of new short codes is noted as temporarily on hold.

Two-way SMS architecture

Customer texts dedicated number
             |
       Incoming SMS event
             |
      Messaging infrastructure
             |
      Queue / processor / API
             |
      Support inbox or workflow
             |
      Authorized SMS reply

AWS can integrate inbound SMS with event services and application functions. The architecture needs consent controls, deduplication, routing by conversation, security protections and observable delivery states. A number's country-level support does not eliminate provisioning requirements for that exact number.

What DryRun actually does

The official SendTextMessage API supports DryRun=true. AWS validates the request but does not send to the destination and does not charge for that dry-run SMS. It cannot demonstrate that a carrier will deliver a later live message or that Spain's alias registration is complete.

aws pinpoint-sms-voice-v2 send-text-message \
  --destination-phone-number "+34600000000" \
  --message-body "Technical validation only" \
  --message-type TRANSACTIONAL \
  --dry-run \
  --region eu-west-1

The number is fictional. Appropriate permissions and eligible origination identity configuration are required; specify --origination-identity when needed. A custom application's “simulation” option should not be assumed to call AWS's DryRun parameter unless its implementation is verified.

Multi-tenant services, sender ownership and safety

A software platform that sends on behalf of multiple businesses must distinguish the technical operator from the legal holder of the sender identity. Registration needs proper entitlement, authorised origin providers and country-specific compliance. A generic shared alias is not automatically a lawful replacement for each customer's business identity. Keep tokens and identifiers private, enforce consent and opt-outs, establish spend caps, and test real delivery only once country and account requirements have been satisfied.

Final checklist

Confirm sandbox status, recipient verification, region, origination identity eligibility, CNMC registration status, authorised providers, delivery-event telemetry, spending limits and privacy rules. For a dedicated number, verify send and receive support before committing to recurring charges. A test API response should never be represented as proof of actual delivery.

Conclusion

An accepted SMS API request, an authorised sender identity and a delivered message are separate events. Spain's alias registry makes that distinction especially relevant. Registered brand names can serve one-way notification use cases; confirmed two-way dedicated numbers can support conversations; DryRun provides safer technical validation without delivering a text. Choose deliberately and document every step.

Official sources

• CNMC announcement, 2026
• AWS Spain sender ID registration
• AWS SMS supported countries
• AWS pricing
• AWS SendTextMessage and DryRun