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SMS Guidelines

When sending A2P SMS internationally, you must comply with destination-country requirements and, in some cases, mobile network operator–specific rules. These requirements vary by market and can affect message delivery, sender ID usage, content, and registration obligations.

Because these regulations are defined by local authorities and operators, they can change at any time and are outside Retarus’ control. Changes may also affect existing SMS configurations. To help ensure continued compliance and delivery, review the country-specific information in this guide regularly. Retarus may update this information without prior notice.

General sending recommendations

Sending A2P SMS successfully across international markets requires careful attention to local regulations. While requirements differ by country, many follow similar principles. Retarus recommends following the guidance in this section to reduce the risk of blocked traffic, compliance issues, or delivery failures.

Compliance

Retarus recommends that you have your intended use cases reviewed by qualified legal counsel to confirm compliance with all applicable laws and regulations.

In some countries, the following content or practices are strictly prohibited:

  • Gambling-related content, such as betting odds

  • Lottery-related content

  • URL shorteners, such as bit.ly or tinyurl

SMS best practices

Follow these best practices to improve delivery and reduce compliance risk:

  • Obtain opt-in consent from each end user before sending messages. Consent may be collected through a website, app, paper form, or SMS opt-in flow.

  • Provide opt-out functionality in all SMS campaigns, including support for STOP.

  • Support HELP and STOP keywords in the end user’s local language where required.

  • Send messages only during the recipient’s daytime hours unless the message is urgent.

  • Do not contact recipients listed on do-not-call or do-not-disturb registries.

  • Do not use a mobile network operator name, sensitive sender IDs such as Police, or a company name that is not your own.

  • Avoid alphanumeric sender IDs made up only of numbers. These may be interpreted as long codes and become subject to country-specific long-code rules.

  • Avoid content related to high-risk financial services, lead generation, debt collection, or debt forgiveness.

📌 Countires not listed

For information about SMS sending regulations in countries not listed in this section, contact your Retarus representative or email support@retarus.com.