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Recommendations to avoid any blocking of SMS sendings

Due to the increase in SMS fraud (smishing) and also the rise of SMS marketing in recent months and years, filters have been implemented to detect mass SMS messages and block those that go against the regulations and laws in force in each country.  In this article, you will find recommendations to avoid any blocking of SMS messages.

To preserve the security of communications and also mobile users, many official bodies regulate telecommunications in most countries.

16 minutes of reading
Publication: 11.10.2023
Última modificación: 11.10.2023

In this sense, mobile phone operators are implementing technology (in the form of filters and detectors) to comply with current legislation about SMS messages.

Below we explain what types of messages are most likely to be blocked and the recommendations to avoid any blocking or rejection.

What is a bulk SMS block or rejection?

Depending on several parameters (number of messages sent, keywords, links, reiteration, sender, etc.) the telephone operators detect campaigns or mass mailings. If these messages are suspicious or directly violate any of the regulations in force in the country of destination, the messages are rejected and are not sent to the final recipients.

Some of them can even be validated by the operators (Delivered or Approved status). In this way, the telephone operators do not give "clues" to possible offenders so they do not implement a trial-and-error technique to avoid the filters.

In general, any rejected or blocked message has a cost since the delivery management has been carried out. In addition, depending on the seriousness of the infraction or blockage, they may incur permanent blockages or generate economic sanctions and initiate a legal process based on the broken regulations or legislation.

What content or type of SMS messages are likely to be rejected or blocked?

The content or type of messages not allowed varies depending on the country of destination and depending on the telephone operators and their filters.

Some of the content that may be subject to blocking are:

  • Classified content without a valid origin. Especially those contents related to official bodies, financial entities, or recognized brands.
  • Political content. In general, or during a period such as electoral campaigns or days of reflection.
  • Unwanted content. Mass messages that do not have the consent of the final recipients.
  • Content not allowed. In many countries, some types of mass messages are not allowed, such as religion, sex, drugs, gambling, alcohol, etc.
  • Invalid links. SMS message containing links that direct the user to suspicious resources (executables, compressed documents, etc.) or domains with low reputation.
  • Fraudulent content. Any message that violates laws and is intended for any malicious activity such as identity theft, fraud, harassment, illegal data collection, etc.

Recommendations to comply with the law and avoid any blockage

Below we present a series of recommendations to take into account to comply with the law and avoid any SMS blocking or mass rejection. These measures are presented in three blocks in order of importance.


SMS Regulatory Bodies

First of all, we always recommend that any company find out if the mass messages or SMS campaigns it sends are accepted according to the regulatory body of the country. Specifically, you should consult the Law that regulates SMS communications in each country and contact the responsible body if there is any doubt or query in this regard.

These are the regulators of communications (including SMS messages) by country:

* In the event of any infraction, these organizations can sue (LabsMobile) for the data and identification of the origin and sender of the messages that do not comply with the regulations. Being possible a sanction or administrative/judicial processes.

ArgentinaEnte Nacional de Comunicaciones (ENACOM)

Ley Argentina Digital

Ley 27.078

Protección de Datos Personales

Ley 25.326

ChileMinisterio de Transportes y Telecomunicaciones, a través de la Subsecretaría

de Telecomunicaciones (SubTel)

Ley General de Telecomunicaciones

Ley Nº 18.168.

Protección de Datos de Caracter Personal

Ley 19.628

ColombiaComisión de Regulación de Comunicaciones (CRC)

Ley del Sector de las Tecnologías de la Información y las Comunicaciones - TIC

Ley 1978 de 2019

Protección de Datos Personales

Ley 1581 de 2012

EspañaComisión Nacional de los Mercados y la Competencia (CNMC)

Ley General de Telecomunicaciones

Ley 9/2014, de 9 de mayo

Protección de Datos Personales

Ley Orgánica 3/2018, de 5 de diciembre

Estados Unidos de AméricaComisión Federal de Comunicaciones (FCC)

Telephone Consumer Protection Act

47 U.S.C. § 227

California Consumer Privacy Act (CCPA)


EuropaInstituto Europeo de Normas de Telecomunicaciones (ETSI)

Normativa europea sobre telecomunicaciones

Comunicado del 21 de diciembre de 2020

Protección de las personas físicas en lo que respecta al tratamiento de datos personales.

Reglamento (UE) 2016/679 de 27 de abril de 2016

MéxicoEl Instituto Federal de Telecomunicaciones (IFT)

Ley Federal de Telecomunicaciones y Radiodifusión

Decreto del 14 de julio de 2014

Ley Federal de Protección de Datos Personales

Nueva Ley DOF 05-07-2010

PerúOrganismo Regulador de las Telecomunicaciones en Perú (OSIPTEL)

Leyes que regulan las telecomunicaciones en Perú


Ley de Protección de Datos Personales

Ley N° 29733


Personal Data Protection Laws

Secondly, comply with all the requirements regarding the protection of personal data (LOPD or GDPR) and have the consent (opt-in) of the recipients. In any country, there is also legislation in this regard and we recommend knowing it and complying with it scrupulously.

In most of these legislations the following points are included:

  • Under no circumstances should third-party or illicitly purchased databases be used.
  • Explicit and demonstrable consent must be requested for the content and type of SMS message to be sent.
  • It is necessary to identify who is the sender of the messages. The addressee must know or, failing that, know who the origin of the communication is without any ambiguity.
  • The methods of unsubscribing from the service with easy and immediate processing.
  • Contact method is readily available to clear up any conflict, unwanted registration, or unidentified communication. These contact methods can be included in the same message or attached resources (web, documents, etc.) such as email, telephone, WhatsApp, etc.
  • Compliance and revision of the Robinson List (users who do not wish to receive any commercial communication).


Recommendations for carrying out a Massive SMS campaign

Thirdly, and after complying with the first two points, it is important to follow some recommendations when carrying out the campaign or sending mass SMS:

  • The mobile database must be cleaned or purged, eliminating all those that do not comply with the mobile number format, those that are inactive or have generated errors in previous sendings.
  • Make sure that all those users who have unsubscribed (appear in the BlackList of the LabsMobile account) are not in the list of recipients. In addition to reviewing the contact list with the Robinson list periodically.
  • It is also recommended to perform initial content tests to avoid any disallowed words or terms.
  • Another recommendation is to carry out incremental mass mailings. That is, start sending with a few hundred, then with a few thousand, and continue with more massive messages if there has been no problem.
  • Lastly, it is suggested to defer the campaigns on different days or during hours on the same day. This functionality has been added to the LabsMobile platform and allows you to send mass messages at X intervals and choose a few minutes between each interval.

Benefits of following the legislation and good practices

These are some of the benefits of following these recommendations explained here:

  • Do not incur any penalty.
  • Not experience any SMS blocking or bulk rejection.
  • Have greater effectiveness in sending since everyone has consented to the communications.
  • A lower-cost in sendings by sending only to valid recipients who meet all the requirements.
  • Greater control of campaigns by performing incremental and/or deferred tests.
  • Have a mobile database that is always updated and valid. Being this resource is a great asset for any brand or organization.

Recommendations to avoid any blocking of SMS sendings

Thus, it should be remembered that most countries choose to follow the legislation with the reference framework of Europe or America.

Our team advises you

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