Limitations sending SMS messages to Indian mobile devices

Twilio SMS messages sent to Indian mobile phones have a number of limitations and requirements due to local government regulations. Please continue reading to learn the difference between each type of SMS message, and what their limitations are.

Indian SMS Types

Twilio SMS messages that terminate in India are classified in one of three categories:

  • Promotional: Marketing messages, advertisements, or anything else that is not considered “Transactional” or “International”.
  • Transactional: Two-factor authentication (2FA) or one-time password (OTP) codes, account or transaction alerts, banking notifications, etc.
  • International: Over-the-top (OTT) messaging traffic (SMS alternatives like Facebook messenger, WhatsApp, Hangouts, iMessage, etc.) that originates outside India, but terminates in India.

Promotional SMS

By default, all SMS messages sent from Twilio phone numbers are categorized as “Promotional”, and are subject to the following limitations:

Promotional SMS can’t be sent to any phone number in India’s Do Not Call (DND) Registry

If you’ve been having trouble sending SMS messages to an Indian number, it may be because that number is registered on the National Do Not Call (DND) Registry. You can find out if a number is on the registry by entering the number (without "+" sign or leading country code) in the search tool here.

If the owner of the phone number wishes to start receiving SMS messages from Twilio, they can update the DND settings by following these instructions published by India's telecom regulator.

The sending phone numbers are changed to the format “XX-NNNNNN”

The sending phone numbers are altered before SMS messages are delivered to end users. Instead of your Twilio number, end users will usually see a random short code with two letters at the front to signify the provider and area code. Due to the sender ID change, recipients are unable to send a reply back to your Twilio phone number; SMS messaging to India is 1-way only.

Messages 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.

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 avoid potential SMS flooding. If you have a need to send identical messages more frequently than this rate, consider purchasing additional Twilio phone numbers.

Transactional SMS

In order for a message to be classified as Transactional, it must meet the following requirements:

  • Message content must be transactional-only: Two-factor authentication (2FA) or one-time password (OTP) codes, account alerts, or other messaging that is directly related to a business interaction between the customer and the service.
  • Starting in March 2019, messages must also use a pre-registered whitelisted SMS message template. All your messages sent to India from your Twilio Account SID must match the templates you provide to us; violation of this rule may result in penalties, including blocking of your registered Sender ID by Twilio or fines passed on to you from the carrier.
  • Messages must come from a pre-registered alphanumeric sender ID.

Additionally, transactional messages do not have the same limitations as Promotional messages. Transactional messages bypass the DND database, and can be received by end-users at any time of day.

Users with a transactional SMS use case can request to pre-register an alphanumeric sender ID directly with Twilio. To begin your pre-registration request, please collect the following information:

  • Company Name
  • Company Website
  • Company Address
  • Is your company headquarters located in India, or outside India?
  • Your email address
  • Twilio project Account SID
  • Estimated monthly volume of messagesA list of three separate 6-character alpha (no numbers) sender IDs, in order of preference.
    • Provide a brief description of sender IDs listed – why were they chosen?
  • Templates for all SMS messages you will be sending to India.
    • Note: Message content must mirror confirmed whitelisted templates as strictly as possible
  • Please describe the details around your use case. This is reviewed by the approving carriers, so kindly provide as much detail as possible.
  • Please confirm that this use case will apply to all messages sent to India from this project.
  • Please acknowledge that if you need to send promotional (non-transactional) messages to India, you will need to use a different Twilio project or subaccount.

Once you have collected this information, please contact our Support team and submit your request.

International SMS

All over-the-top (OTT) messages (SMS alternatives like Facebook messenger, WhatsApp, Hangouts, iMessage, etc.) originating outside of India must be submitted through mobile carriers’ dedicated International Long Distance Operator (ILDO) connections. These messages have to be terminated with either a short code or a long number. OTT messages can not be sent via the conventional promotional or transactional connections like standard SMS; India mobile carriers are actively blocking OTT messages submitted through these non-authorized connections. For more information, please contact our Support team.

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