When building your SMS campaigns, you must stay aligned with best practices and compliance to avoid poor performance.

Many factors influence the optimal delivery of your messages, and you should be fully aware of their impact when using SMS as your communication channel.

Poor practices may lead to overcharging and potentially give customers the impression that you are delivering spam, especially if you are sending long messages that are spliced and delivered over several separate messages.

You are advised to follow the guidelines in this section. In addition, make sure that you check out International SMS coverage and Connectivity for full information about local regulations and terms of use.

Invalid Numbers and Format Errors

If you add an invalid or incorrectly formatted mobile number in the web interface, the system will detect it and will stop messages from being sent to them. This stops you from being charged for a message which will never be received.

This is an additional service offered by Infobip which enables you to clear and tidy up your number database. It is recommended to use it periodically to boost deliverability and improve campaign results through higher delivery rates.

Duplicate Messages and Numbers

In your campaigns, you should not send a message multiple times to a single number.

If you set up your campaign to send the same message to the same number twice, when the campaign is launched, the Infobip web interface will detect the duplicate message and won't send it again.


The duplicate messages and numbers feature is available only with the Infobip web interface and not via the API.

Number Formatting

It is strongly recommended to use the E.164 number format. E.164 numbers are internationally standardized to a 15-digit max. length.

Phone numbers must start with a country code, followed by a network code, then the subscriber number. Plus prefixes + are not required.

Phone numbers that are not E.164 formatted may work, depending on the handset or network.

Example: a Croatian number is formatted as 385981234567, while a UK number is formatted as 447712345678.


All phone numbers and email addresses that no longer want to be contacted are stored inside the Do Not Contact list. This feature, sometimes called Blocklist, ensures that no communication is sent to those people who have opted out of your communication campaigns. It enables you to remain compliant with important personal data regulations such as GDPR, and always be able to track whether a person who wants to stop receiving communication from your company is really on your Do Not Contact list.

If you manage multiple accounts, you can select a specific account for the blocklisted records. From that moment on, when you try to send messages to a blocklisted record, our platform rejects this message and prevents any unwanted communication from being sent.

Blocklists can be created or added in the following ways:

  • Blocklist API (opens in a new tab) using Create blocklists (opens in a new tab).
  • Manually over People data platform using the Do Not Contact list.
  • Automatically over Moments communication flow - the blocklist record is automatically created once an end user unsubscribes by replying with a specific keyword (for example, STOP). This is available with the channels: SMS and MMS.
  • URL_OPTOUT - the blocklist record is automatically created once an end-user clicks an opt-out link included in the message.
  • CAMPAIGN - the blocklist record is automatically created through a triggered event in the Flow (for example, if the message was not opened in 24 hours, it is added to the blocklist).

Add a person to the blocklist

You can add a Person to the Blocklist either manually or automatically.

Manually add a person to the blocklist:

  1. Log in to the web interface.
  2. On People, go to the Configuration tab.
  3. Select the Do Not Contact list to see unsubscribed users.
  4. Add new contacts or import a list of people who no longer want to receive your communication.

Automatically add a person to the blocklist:

  1. Go to Moments and create your communication.
  2. Select the element called Add to Do Not Contact list.
  3. Validate and launch. If the customer replies with a certain text or performs a certain activity, this element is activated and the customer's number or email is blocklisted.

Add a person to the blocklist over API:

  1. Use the Blocklist API (opens in a new tab).
  2. Programmatically manage and track the list of recipients who want to stop receiving communication from your company, remaining compliant with important personal data regulations, such as GDPR.

Blocklist guidelines

Note the following usage guidelines for blocklists:

  • Main account can access the blocklist for mainand subaccounts
  • Subaccounts can only access a blocklist for subaccounts
  • Blocklist can be created for a sender, either numeric or alphanumeric
  • Number of destinations cannot exceed 50000 (API limit per request)


The destinations that can be blocked include:

Channels supporting blocklists

The channels used for sending for which blocklist is supported:

  • SMS
  • MMS
  • Viber
  • RCS
  • Email

Roaming Numbers

When launching a campaign, there is a possibility that the recipient will be in roaming. All efforts will be made and the platform will forward these messages further to reach the recipient, however, the delivery in such situations can't be guaranteed.

Scheduling Messages

Advance message scheduling can be set up using the Infobip API or directly in the web interface.

Use the scheduling options in the web interface when creating campaigns to specify start and end times according to time zones.

Scheduling through HTTP API requires Client to set * sentAt* to the desired value (2015-07-07T17:00:00.000+01:00)

Scheduling over the SMPP API requires setting * schedule_delivery_time* to the desired value by entering it in the relative time format (“070605040302100R”). This means that the message will be delivered in 7 years, 6 months, 5 days, 4 hours, 3 minutes, 2 seconds and 1 tenth of second from now.

Country-Specific Requirements

See the section on International SMS coverage and Connectivity to find out more about country-specific regulations for sender names, and more.

Long Messages

All SMS messages are charged per message. When you send long SMS messages, they end up being broken up into several messages because of message length restrictions.

This means all of these individual messages which are part of one campaign are being charged individually.

Message length allowances vary between mobile networks. It is suggested to constrain sending to no more than 5-7 long SMS parts. Contact your dedicated Infobip point of contact for more information around specific network limitations.

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