Using the SMTP API


SMS messages are sent by submitting a specially formatted email to the API. Each email can contain up to 100 000 messages/mobile numbers. To send larger numbers of messages, simply send multiple emails with 100 000 messages per email.

A single email can contain one message to all recipients or multiple personalized messages.

We recommend the following:
  • Use plain-text formatted emails (not HTML).
  • To send many messages, use one email (instead of thousands of emails with one message per email).
  • Make use of the reply parameter to have an API response sent to your email address.

Send your first message
  1. Get your API ID from your Developers’ Central account.
  2. Enter the destination mobile number in international format.
    • The mobile number needs to start with the correct country code.
    • It must contain no spaces or other non-numeric characters.
    • If the mobile number starts with a zero, remove the zero before typing the rest of the number
  3. Send an email as per the example below to sms@messaging.clickatell.com.

  • Until you make a purchase, your SMS messages will contain pre-defined content.
  • You can add additional to:xxxx lines to send to more mobile numbers.
  • It is important to set the reply parameter (as per the example above) so that you can receive an automatic response from the API that will contain error messages or tracking IDs for your messages. If the API appears to ignore your email, check that the mail is being sent as plain-text (not HTML) and that the Content-Transfer-Encoding header of your mail is set to 7bit.

Read more about sending basic messages.

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