- When more than 200 SMS/day sent per Long Number.
- When the ratio of incoming to outgoing SMS on a Long Number is more than 1:3 (Outgoing SMS -> Incoming SMS).
- When more than 1 SMS/ 4-second/Long Number sent out (If you require higher throughput, you can purchase more numbers and spread your traffic across your numbers. E.g. 10 numbers = 10 SMS per 4-second).
- 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 bit.ly) 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".