SMS messages entering into India are categorized as “Transactional” or “Promotional”. By default, all SMS messages sent from Twilio phone numbers are categorized as “Promotional” and are subject to the following limitations:
1. They cannot be sent to any phone number in India’s Do Not Call Registry
If you’ve been having trouble sending SMS messages to an Indian number, see if that number is registered on the National Do Not Call Registry.
If the owner of the phone number wishes to start receiving SMS messages from Twilio, they can update the DNC settings by following the instructions on this website.
2. The sender IDs are changed to the format “XX-NNNNNN”
The sender IDs are altered before SMS messages are delivered to end users. End users are very likely to see a sender ID composed of 2 letters followed by 6 numbers instead of the Sender ID you specified. Due to the sender ID change, SMS recipients are unable to send a reply back to your Twilio phone number.
3. They are only delivered between the hours of 9 A.M. and 9 P.M. local Indian time
If you’ve been seeing delivery delays when sending to Indian numbers, make sure you are making the requests during the operational hours of 9 A.M. to 9 P.M., as overnight messages are likely to be cached until the next day.
4. No more than one message every 20 minutes from the same Sender ID to the same destination number with the same message body
This is to to avoid potential SMS flooding. If you have a need to send identical messages more frequently than this rate, consider getting more Twilio numbers.
Please note that the above limitations are regulations set up by the government of India. If the above still doesn’t explain the issue you’re running into when sending SMS to India, please contact us, we would love to help.