As of 15 September 2026, CNMC (Comisión Nacional de los Mercados y la Competencia), introduces new requirements. Any SMS or RCS message sent to Spanish (+34) numbers using an unregistered alphanumeric Sender ID will be automatically blocked by local operators.
The new requirements follow a growing global trend towards stronger sender verification for business messaging.
All businesses sending Application-to-Person (A2P) SMS messages to Spanish mobile subscribers using an alphanumeric Sender ID must ensure their Sender IDs are registered and approved before enforcement begins.
Numeric sender IDs (VMNs and short codes) are not affected by this regulation.
What is a Sender ID?
A Sender ID is the alphanumeric name shown as the sender of an SMS message, such as a brand or organisation name.
It is the unique identification that appears on the recipient's mobile device as the sender of the message, enabling recipients to recognise the origin of the message and supporting trust.
Sender ID requirements
Sender IDs used in Spain must meet the following requirements:
The requested Sender ID must have a direct link to the company such as the company name, a trademark or website domain.
Sender IDs are case sensitive.
Sender IDs must be between 3 and 11 characters long.
Sender IDs must clearly identify and relate to the company, brand, service, or organisation using them.
Businesses must have the right to use the Sender ID they are registering.
A short business justification describing the intended use of the Sender ID is required as part of the registration process.
Sender IDs may contain:
Letters: A-Z, a-z, Ñ, ñ, Ç, ç
Numbers: 0-9
Spaces (not consecutive and not at the beginning or end)
Special characters: @, &, -, _, ., +
Sender IDs must not be purely numeric and must not resemble a phone number or short code.
Consecutive spaces are not permitted.
Spaces at the beginning or end of a Sender ID are not permitted.
Sender IDs must not contain accented characters, including:
á, é, í, ó, ú
Sender IDs must not contain the following special characters:
¡ ! # % ( ) * , / : ; < > = ? [ ] €
Generic Sender IDs that do not clearly identify a brand or organisation may be rejected. Examples include:
Message
Bank
Flight
Urgent
INFO
SMS
Sender IDs containing offensive or discriminatory language are not permitted.
Sender IDs that may confuse recipients or impersonate another organisation, brand, or entity are not permitted.
Sender ID registration process
There are three ways to register an alphanumeric Sender ID for use in Spain, depending on whether you would like to manage the registration yourself or have Dotdigital assist you.
Option 1: Self-registration with CNMC
You can register your Sender ID directly with CNMC through their registration portal.
To complete the registration, you need:
A valid Spanish digital certificate.
The required Sender ID and business information.
Any supporting documentation requested by CNMC.
For step-by-step guidance, refer to our Spain Sender ID Self-Registration Guide.
Once your Sender ID has been approved by CNMC, notify Dotdigital so we can enable it for use in your Dotdigital account.
Option 2: Dotdigital submits the registration request on your behalf
Dotdigital can submit the Sender ID registration request to CNMC on your behalf.
To use this option:
Complete the Spain Sender ID Registration Request Form.
Dotdigital submits the registration request to CNMC.
CNMC reviews the application and verifies that it meets the applicable requirements.
CNMC contacts the Authorised Representative to approve the registration.
Important
The Authorised Representative must have a valid Spanish digital certificate to access the CNMC portal and approve the registration request. Once notified by CNMC, the Authorised Representative has 10 days to complete the approval process. If approval is not completed within this timeframe, the registration request may be rejected.
Once approved, the Sender ID becomes eligible for use when sending SMS messages to Spanish mobile subscribers. Notify Dotdigital so we can enable it for use in your Dotdigital account.
Option 3: Dotdigital submits and authorises the registration on your behalf
If you do not have access to a Spanish digital certificate, Dotdigital can submit and authorise the registration on your behalf, subject to the appropriate authorisation being provided.
To use this option:
Complete the Spain Sender ID Registration Request Form.
Complete and sign the required Letter of Authorisation (LOA).
Dotdigital submits the registration request and completes the authorisation process with CNMC on your behalf.
CNMC reviews the application and verifies that it meets the applicable requirements.
Once approved, the Sender ID becomes eligible for use when sending SMS messages to Spanish mobile subscribers.
Registration review and activation
CNMC reviews submitted Sender IDs and verifies that:
The Sender ID clearly identifies the business, brand, service, or organisation.
The organisation has the right to use the Sender ID.
Supporting information is accurate and complete.
The Sender ID complies with the registration requirements.
Businesses should allow sufficient time for registration, review, and activation before planning SMS campaigns.
What happens if a Sender ID is not registered?
If an alphanumeric Sender ID is not registered, SMS and RCS messages sent to Spanish (+34) mobile numbers will be automatically blocked by local operators and will not be delivered to recipients.
Global trend
Spain is not alone. The Sender ID registration approach reflects a broader international move towards sender verification:
Singapore – introduced in 2023.
Ireland – introduced in 2025.
Australia – introduced in 2026.
Austria – introduced in 2026.
United Arab Emirates – alphanumeric Sender ID registration has been in place for many years.
Questions about Sender ID registration?
If you have questions about Sender ID registration or SMS sending in Spain, contact your Customer Success Manager or email us at support@dotdigital.com.