Spanish mobile operators have been blocking SMS, MMS and RCS messages with unregistered alphanumeric sender IDs since September 15th, 2026. For brands sending to customers in Spain, the question is no longer whether to register, but whether your registration is actually complete, correct and linked to the provider carrying your traffic.
The key is making sure your registration is fully in place. A last-minute change to the rules means thousands of aliases are currently running on a temporary permission rather than a finished registration. If your Spanish traffic is still flowing today, it’s worth confirming that Spanish sender names are fully registered.
Where things stand in October 2026
Operators check the CNMC’s alias database before delivering a message, and messages that fail the check never reach the customers.
Shortly before the deadline, the CNMC faced a large backlog of applications it could not process in time. Circular 3/2026 created a transitional arrangement: aliases whose applications were already submitted and pending when blocking began may continue to be used while the regulator works through them. This provisional permission ends when the CNMC approves or rejects the alias, or when the deadline for the alias holder to confirm the application runs out, up to a maximum of three months from notification. For many brands, that window closes in December 2026.
This means senders have to consider these two aspects:
- Traffic arriving today does not prove your registration is finished. You may be running on the transitional permission.
- An unanswered authorisation request can end that permission early. If your provider or agency submitted on your behalf, someone at your organisation must confirm it in the CNMC portal. If nobody does, the application lapses and the alias stops working.
The three ways a message gets blocked
Operators apply the same filter to every message with an alphanumeric sender ID:
- The alias isn’t in the registry. Any brand name, trade name or abbreviation not listed is blocked.
- The traffic came through a provider not authorised for that alias. Each registered alias names the Origin Provider(s) permitted to originate it. A correctly registered alias sent through an unlisted provider is still blocked.
- The sender isn’t authorised by the alias holder. Agencies, CRM platforms, subsidiaries and franchises need express authorisation from the brand that owns the name.
The second point is the one that catches established senders. Brands that registered in the spring can still lose delivery by moving a campaign to a different platform, adding a backup route, or letting an agency send through its own connection.
How to check your registration
Look up your own aliases. The CNMC publishes a public search where anyone can check whether an alias is registered and who holds it, at numeracionyoperadores.cnmc.es/alias. Search every sender name you use for Spain.
Check the exact string. Aliases are case-sensitive and registered exactly as submitted. “MyBrand”, “MYBRAND” and “My Brand” are three different aliases and each needs its own entry. Check abbreviations, local-language variants, campaign-specific senders and anything a regional team set up independently.
Confirm which providers are linked. For each alias, verify that every provider that may originate your Spanish traffic is registered and authorised on that alias, not just your main one.
Check for pending authorisation requests. Ask whoever holds your digital certificate to log into the CNMC portal and look for outstanding confirmations.
Ask your messaging provider for Spain delivery data. Compare recent delivery rates for Spain against another European market. A gap that appeared after September 15th points to a registry problem rather than a general deliverability issue.
What a blocked alias looks like from inside the business
Blocked traffic leads to specific problems customers may face:
- Banking and fintech: customers report that one-time passcodes never arrive. Login and payment-confirmation funnels drop off in Spain only, and contact-centre volume rises.
- Delivery and logistics: dispatch and “driver is nearby” notifications stop landing, pushing recipients to call support or miss deliveries.
- Retail and e-commerce: a campaign goes out with normal send volumes but near-zero engagement from Spanish recipients.
- Travel: check-in reminders, gate changes and booking confirmations fail at exactly the moment customers need them.
- Healthcare: appointment reminders don’t arrive, and no-show rates climb.
Because only Spain is affected, aggregate reporting can hide the problem for weeks. Segment your delivery metrics by country before assuming everything is fine.
Don’t forget RCS
The registry covers RCS as well as SMS and MMS. If you run RCS Business Messaging campaigns to Spanish customers, your RCS sender needs to be registered too, and RCS aliases follow their own length rules, allowing considerably longer names than the 11 characters available for SMS.
This is worth planning around rather than treating as paperwork. RCS already gives customers a verified sender, a brand logo and a colour scheme in the native messaging app. Combined with a registered alias in a national registry, Spanish recipients get two independent signals that the message is genuine, at a time when roughly half of consumers in Spain have received fraudulent SMS messages. Brands launching RCS in Spain should build registration into the launch timeline, since an agent that isn’t registered can’t send under its own name.
If an alias is blocked right now
Register it, and treat the gap as an operational incident. While approval is pending, critical traffic such as one-time passcodes can be sent from a numeric sender so that customers aren’t locked out of their accounts. It is not a good long-term answer, because an unfamiliar number is exactly what customers have been trained to distrust, but it keeps authentication working. Discuss the fallback with your messaging provider before you need it.
Spain isn’t an exception
Ireland and the Netherlands have introduced comparable sender registries, and similar frameworks are in place in Singapore and other markets. Verified sender identity is steadily becoming the baseline for reaching mobile users in regulated markets. Brands that keep a single, central inventory of their sender names, the evidence behind them and the providers authorised to use them will find each new market straightforward. Brands that handle registration country by country, team by team, will keep rediscovering the same problem.
How iBASIS Business Messaging supports your Spanish traffic
iBASIS is a participating aggregator in Spain’s CNMC alias ecosystem. Brands registering through the CNMC portal can select iBASIS Netherlands as their Origin Provider, which makes iBASIS an authorised route for their SMS, MMS and RCS traffic to Spanish subscribers.
Beyond Spain, iBASIS supports enterprises with global SMS and RCS connectivity, direct operator routes, API integration, per-market delivery reporting and guidance on sender requirements in regulated markets.
If you’re unsure whether your Spanish sender names are fully registered and correctly linked, talk to us before the transitional window closes.