The following are the usual characteristics of A2P SMS, which when present will be blocked by carriers:

  1. When more than 200 SMS/day sent per Long Number.
  2. When the ratio of incoming to outgoing SMS on a Long Number is more than 1:3.
  3. For destinations other than US/ Canada: Messages can be blocked if sent more than 1 SMS/ 4-second/Long Number.

        Note: Carriers further dequeue the message at a much lesser pace based on the number of Units

(If you require higher throughput, you can purchase more numbers and spread your traffic across your numbers. E.g. 10 numbers = 10 SMS per second).

        4. When the same message sent to the same user within 5-10 seconds of the first message.

SMS Content which can be blocked by carriers:

  • When using repetitive URL's and keywords, shortened links(such as in the SMS content.

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: "this caller id is not allowed for outbound message".