What are the limitations and restrictions on US long code SMS messages?

Long codes are regular 10-digit US/Canada phone numbers that can make and receive voice calls as well as SMS messages. Long codes are meant for person-to-person communication. Long-codes are not recommended for bulk messaging.

The following characteristics of application-to-person SMS messages will cause your message to be blocked by carriers.

  1. When more than 200 SMS are sent per day per long code number
  2. When the ratio of incoming to outgoing SMS on a long code number is more than 1:3.
  3. For destinations other than US/ Canada: messages will be queued if sent more than 1 SMS/4-second/long code number
  4. When the same message is sent to the same user within 5-10 seconds of the first message.

 Other factors that can result in SMS blocking: 

  •   The use of repetitive URL's and keywords or shortened links(such as bit.ly) in the SMS content.
  •   Multi-unit messages. 

Note: When sending SMS to US destination numbers, please use your US long-code number (from Plivo account) in international format. If not, you will get this error message: "This caller id is not allowed for outbound message"

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