Best practice for SMS

SMS best practice focuses on creating clear, relevant, and engaging messages that reach recipients at the right time and encourage positive responses. Following these guidelines helps improve delivery rates, boost engagement, and strengthen customer relationships.

Message content [#message-content]

All SMS messages are charged per message part. When a message exceeds the character limit (160 for GSM, 70 for Unicode), it is split into multiple parts and each part is charged separately. Constrain long messages to no more than 5 to 7 parts.

For details on character encoding and how to optimize message length, see Multilingual SMS.

Delivery [#delivery]

Use E.164 number format [#use-e164-number-format-delivery]

Use the E.164 number format. E.164 numbers are internationally standardized to a maximum length of 15 digits. 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.

Validate numbers [#validate-numbers-delivery]

If you add an invalid or incorrectly formatted mobile number in the web interface, the system detects it and stops messages from being sent. This prevents charges for messages that are never received.

Number Lookup is an additional Infobip service that enables you to clean up your number database. Use it periodically to boost deliverability and improve campaign results through higher delivery rates.

Schedule messages for optimal timing [#schedule-messages-delivery]

Advance message scheduling can be set up using the Infobip API or directly in the web interface. Use scheduling to send messages at times when recipients are most likely to engage, respecting time zones and local sending restrictions.

• HTTP API: Set sentAt to the desired value (for example, 2025-07-07T17:00:00.000+01:00)
• SMPP API: Set schedule_delivery_time using the relative time format (for example, 070605040302100R - 7 years, 6 months, 5 days, 4 hours, 3 minutes, 2 seconds, and 1 tenth of a second from now)

Avoid duplicate sends [#avoid-duplicate-sends-delivery]

Send each message to a number only once per campaign. If you set up your campaign to send the same message to the same number twice, the web interface detects the duplicate and does not send it again.

Account for roaming [#account-for-roaming-delivery]

When launching a campaign, there is a possibility that the recipient will be in roaming. The platform makes every effort to forward these messages to the recipient, but cannot guarantee delivery in roaming situations.