The Spanish CNMC mandates registration of all alphanumeric Sender IDs for SMS, MMS, and RCS to Spanish numbers by 7 June 2026 to prevent fraud. Unregistered aliases will be blocked. Senders must register directly with CNMC using legal details and a digital certificate. Alternatively, using dedicated numeric numbers avoids registration but shows numeric senders. Sinch is the registered Provider of Origin for routing.
What's changing and why
The Spanish National Markets and Competition Commission (CNMC), under Ministerial Order TDF/149/2025, has launched a National Alias Registry for all alphanumeric Sender IDs (aliases) used to send SMS, MMS, and RCS to Spanish mobile numbers.
From 7 June 2026, Spanish mobile operators will block any message sent with an alphanumeric Sender ID that is not registered in this registry. The rule applies to every sender, Spanish or foreign, using an alpha alias to reach +34 numbers.
The registry is designed to reduce SMS impersonation fraud ("smishing"), increase transparency, and give Spanish subscribers a traceable origin for every branded message they receive.
From 28 April 2026 you will be able to register your Sender ID directly with the CNMC, to avoid disruption.
Who this affects
You need to act if all of the following are true:
You send messages to Spanish (+34) mobile numbers, and
You use an alphanumeric Sender ID (for example,
YOURBRAND) as the sender, andYour Sender ID is not already registered with the CNMC.
Sinch is your Registered Provider of Origin (PRO) — the regulated carrier of record. The CNMC requires the alias holder (you) to register each alias directly, because the registry needs your legal entity details, an authorised legal representative, and a digital signature that only your organisation can provide.
Step-by-step registration guide
Before you start - you will need
Your company legal details: legal name, NIF / CIF / VAT ID.
A nominated legal representative: full name, NIF (or equivalent), email, mobile.
An EU-compatible digital certificate for your representative (e.g. FNMT certificate) installed with the AutoFirma signing tool. This is used to sign the submission electronically.
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A list of the aliases you want to register, with:
Channel (SMS, MMS, or RCS)
Use case (e.g. transactional OTP, appointment reminders, marketing)
Activation date and deactivation date (maximum 24 months from activation)
Proof of ownership: trademark certificate, mercantile registry excerpt, domain certificate, or a signed declaration of responsibility
Install AutoFirma and your digital certificate. Download AutoFirma from the Spanish Government's e-administration site and install your FNMT (or equivalent EU eIDAS) certificate for your nominated representative.
To check if your digital certificate is accepted: Install AutoFirma software on your computer:Firma Electrónica | Descargas -Ciudadanos Validate your certificate here:VALIDe If your certificate is not accepted, you can request one at: Certificación Digital - FNMT .
Outside the EU?
You do not need to be EU-based to register. The FNMT (Spain's certificate authority) issues digital certificates to foreign entities.
What's required: your company documentation (certificate of incorporation, power of attorney) must be apostilled under the Hague Convention and translated into Spanish by a sworn translator. Allow 6-8 weeks for certificate issuance. Start now.
Quick test: visit tramites.cnmc.gob.es/formulario/213. If the form loads, you're good. If not, your certificate isn't installed or isn't compatible.
Alias naming rules (CNMC)
Length: 3 to 11 characters
Allowed: a–z, A–Z, ñ/Ñ, ç/Ç, 0–9, space, and
@ & - . +Not allowed: leading/trailing or consecutive spaces, accents,
# % ( ) , / : ; < > = ¡ ! ¿ ? [ ] €, or an alias that is only digitsProhibited: impersonating public authorities, trivial variants of existing registered aliases, or aliases not linked to your brand, domain, or legal entity
Steps
For both existing and new sender IDs (Alias)
Open the CNMC registration form. Go to tramites.cnmc.gob.es/formulario/213 and select the alias registration procedure.
Identify the alias holder. Enter your company legal name and NIF/CIF/VAT ID. The holder must be the legal entity that owns the brand represented by the alias.
Identify the legal representative. Enter your representative's name, NIF, email, and mobile. This is the person who will sign the submission with AutoFirma and who will receive authorisation requests.
Select your Provider of Origin (PRO). Choose SINCH SPAIN from the PRO dropdown. This tells the registry that Sinch is the carrier routing your traffic.
Enter each alias. For every alias, provide the channel (SMS / MMS / RCS), use case, activation date, deactivation date, and attach proof of ownership.
Sign and submit with AutoFirma. The form will hand off to AutoFirma to apply your representative's digital signature. Submit.
Authorise within 10 working days. After submission, the representative receives an authorisation request. If it is not authorised within 10 working days, the registration auto-declines and you must start again. Add a reminder.
Confirm status. The CNMC will notify you of approval. Keep the confirmation for your records and let us know once you have completed the registration.
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After registration. Once the CNMC confirms your registration, email the confirmation to: internationalsending@messagemedia.com
Include your account name, the registered alias(es), and the CNMC confirmation. We need this to activate the alias on our platform.
Alternative: move to a dedicated Spanish number
If you cannot complete registration by the deadline, for example, because you are outside the EU and cannot obtain an eIDAS digital certificate in time, or your legal process cannot move fast enough, you have a clean fallback:
Switch your Spain traffic to a dedicated number.
Numeric senders are not covered by the CNMC alias registry and will continue to deliver to Spanish mobile numbers without registration.
What you get:
Uninterrupted delivery to Spain past 7 June 2026 with no registration burden.
A dedicated number that your recipients can reply to — useful for two-way use cases.
No AutoFirma / digital certificate requirement.
Trade-offs to consider:
Messages will display a numeric sender rather than your brand name.
There is a monthly rental for dedicated numbers
Opt-out and content rules for Spanish numeric traffic still apply.
How to request a dedicated Spanish number:
Log in to your Sinch MessageMedia account and navigate to Settings > Numbers > Dedicated Numbers
Click Add a Number
Frequently asked questions
Do I need to do anything if I only send to Spain from a numeric sender today? No. Numeric long codes and short codes are not covered by the registry.
Can Sinch register on my behalf? The registry requires your legal entity details and a digital signature from your nominated representative. That signature cannot be delegated to us. Registering directly is the Sinch-recommended path and the fastest.
What happens on 7 June 2026 if I don't register? Spanish mobile operators will reject messages sent with any unregistered alphanumeric Sender ID. You will see delivery failures until the alias is registered or the traffic is moved to a numeric sender.
My organisation is outside the EU. Can I still register? Yes, but your representative still needs a digital certificate compatible with the Spanish AutoFirma signing tool (typically an eIDAS-recognised certificate). If this is a blocker, the dedicated-number alternative in section 5 is the recommended fallback.
How long is a registration valid for? Up to 24 months from the activation date you nominate. You can renew before expiry.
Can I register the same alias for SMS and RCS? Yes, but each channel is registered separately within the same submission.
Need help?
International Sender Team: For Sender ID (Alias) registration inquiries Email: internationalsending@messagemedia.com
CNMC form: tramites.cnmc.gob.es/formulario/213