India SMS Features and Restrictions


Vonage supports Domestic and International enterprise SMS business to India.

To follow the regulations of the Telecom Regulatory Authority of India (TRAI), domestic enterprises can only submit A2P SMS through domestic connections to end recipients after successful registration with Distributed Ledger Technology (DLT).

DLT aims to create a cleaner and transparent system in the Indian telecom industry and curb Unsolicited Commercial Communication (UCC) and an enhanced mobile subscriber policy. Information on the regulation can be reviewed here.

Any enterprise that fails to pre-register Distributed Ledger Technology (DLT) will become non-compliant and will not be able to send A2P SMS to end recipients via domestic connections.

International Enterprises are not affected by this change.

DLT Implementation History

Phase 1 - Sender ID/Header Scrubbing

  • Live since 1st June 2020.
  • Only DLT-registered Sender IDs can terminate SMS on domestic routes.
  • Entity Registration and Header Registration mandatory.

Phase 2 - PEID/Entity Unique ID Scrubbing

  • Live since 19 November 2020.
  • PE ID is mandatory to provide along with the Header for successful SMS termination.
  • Entities have to start registering their Content and Consent Templates on the DLT Portal on which they have registered their entities.

Phase 3 - Template/Content Scrubbing

  • Live since 1 April 2021.
  • Only DLT-registered Templates, along with Sender ID and PEID able to terminate SMS on domestic routes.
  • Similar to the Sender ID upload process, you need to upload these templates with any one operator DLT portal.
  • Brand Name is mandatory to be included in the template registration content.

Phase 4 - Consent Upload in DLT

  • Live since 15th July 2021.
  • Need to register the Consent Templates with any of the approved DLT portals. After the consent templates are approved, they will get synced across the rest of the DLT Platforms.

DLT Requirements

  • It is mandatory to have a brand name in all categories of messages.
  • The exact text should match from your application to suppliers to the DLT Platform.
  • Only Approved Templates should be submitted to Vonage.
  • Header Mapping against each template should be verified.
    • Where header ‘X’ is mapped on the DLT platform with a ‘Y’ text, then it should be used accordingly.
    • If you wish to use any other header, changes on the DLT platform should be done accordingly.
  • The variable length should not exceed 30 characters.
    • 30 characters per variable including the spaces and the content templates can be registered with variables in GSM (English) characters and in unicode (for local dialect characters).
    • If it is more than 30, you will need to add more variables.

Registering for DLT

To send any SMS through domestic connections, all enterprises must register their Principal Entity, Headers, Templates with the Brand Name, and provide consent on one of the approved DLT systems:

Maintaining Compliance While Submitting Messages to the Vonage Platform

After you have registered for DLT with one of the portals, there are two ways to ensure your traffic is compliant with DLT.

Vonage is not responsible for domestic entities registering for DLT. We do not verify if domestic entities have correctly provided their PEID, Sender ID, and Template IDs.

If a message errors due to these fields not being provided or valid, the carrier does this will be reflected in the Delivery Receipt webhook and SMPP DLR.

You can read a tutorial by our Developer Relations team discussing DLT and how to implement it.

Option 1: Submit Required DLT Parameters with Every Request

  1. Make the necessary changes on your end so that your Entity ID, Sender ID, Header, and Templates (as registered with DLT) are sent with every API submission (see additional properties you must use below).
  2. Inform Vonage in a support request to enable routing for Option 1 for your Sender ID.
  3. Start sending SMS after you have received confirmation routing has been enabled for you.

Option 2: Let Vonage Detect Your Template

  1. Create your DLT Details .csv file.
    • Download the template file from your DLT Portal.
    • Add your details to this file.
    • Save as <entityid>.csv where <entityid> is your Entity ID.
  2. Register for DLT with Vonage by submitting a support request with the following information:
    • Your PEID - Entity unique ID received from DLT after entity registration approved.
    • Entity Name - Company name registered on DLT.
    • Sender Name - Six character alphanumeric Sender/Header, which has been registered and approved in DLT.
    • The name of which DLT system you are registered on.
    • Your DLT details file (mentioned above).

Additional Parameters or Properties to Support DLT

Vonage has added functionality within our Send SMS API endpoint or via SMPP to allow domestic entities to comply with the DLT regulation by providing both their PEID (unique entity ID) and the template ID for every SMS request made.

The API properties used in this endpoint are to be matched exactly as listed below:

  • ‘entity-id’ parameter needs to be the DLT approved PEID (unique Entity ID)
  • ‘content-id’ parameter needs to be the DLT approved Template ID
  • ‘from’ parameter needs to be the DLT approved Sender ID (Header ID)
  • If you use SMPP to send SMS messages with Vonage, the following fields apply:
    • 0x1470 needs to be the DLT approved PEID (unique Entity ID)
    • 0x1471 needs to be the DLT approved Template ID
    • The Sender ID needs to be the DLT approved Sender ID (Header ID)

Vonage Error Codes for DLT Related Issues

Error Code Description
50 DLT entity ID details are missing or wrong (includes null + invalid value)
51 DLT header ID (Sender ID) details are missing or wrong (the Sender IDs must be registered with suppliers but not with DLT platform)
52 DLT content ID details are missing or wrong
53 DLT error for consent
54 DLT generic error

SMS Types

By default, users will fall into the International promotional (SMS without opt-in) category with restrictions as mentioned below.

If you are an International user or have a different SMS type than is listed below, contact your account manager or submit a support request.

Traffic Type Content Allowed Sender ID Restrictions/Regulation
Domestic Transactional Transactional traffic, OTP 6 digit alpha with DLT pre-registration. No restrictions. 24/7 delivery without NDNC restrictions.

Registered Alpha Sender ID will be added with 2 letters as a prefix, depending on which carrier was used to deliver the SMS to the final operator or 2 random numbers; e.g., MD-XXXXXX (where XXXXXX is the registered Sender ID).

Domestic Promotional

(without opt-in)

Promo/Marketing Content 6 digit numeric with DLT pre-registration.

Promo SMS will be blocked to numbers registered in NDNC as per TRAI regulation.
Promo SMS are only delivered between 10am-9pm IST time.
SMS outside the time range will be queued and delivered the next day.

DLR not supported since 9 Oct 2020.

International (transactional/opted-in promo)

International originated transactional content & Opt-in Promo content.

(If the client registered in India, but the SMS message originated from outside India, it will be identified as International traffic).

Sender ID not supported and will be changed to a random short/long virtual number.

For OTP/Transactional traffic mainly. For Opted-in promo, content needs whitelisting through your Account Manager before sending SMS.

SMS Delivered 24/7 via International route.
No restrictions for NDNC listed numbers.

International Promotional (without opt-in) Default route Promo/Marketing Content Sender ID not supported and will be changed to a random short/long virtual number.

Delivery on best effort basis with shared SC from SMS partner.

10am-9pm(IST) delivery to non-NDNC customers only.

DLR supported.

Sender ID

For enterprises that finished the DLT application successfully, the SMS Sender ID will be prefixed with an additional two letters, depending on which final operator the number belongs to. A full list of prefixes can be found here: India Pre-registered Sender ID Prefixes.

Alpha Sender ID is not supported for International customers and will be changed to a random short code.

It is possible to also complete the registration of Alpha Sender IDs to other countries.

Contact your account manager to discuss processing Sender ID registration if you have more than one million messages a month.

Do Not Call Registry/Do Not Disturb Service

Promotional SMS are barred and will get blocked by operators to numbers those registered in the Indian NDNC (National Do Not Call registry).

SMS delivery is blocked between 21:00 – 10:00 hours IST for end recipients who registered with Do Not Disturb Service (DND). This means promotional SMS can only be delivered only between 10:00 - 21:00 hours IST.

Operators do not support delivery notifications for messages sent via promotional routes with numeric headers.

Limitation to Avoid Potential SMS Flooding

Local regulations specify limitations to the number of messages that can be sent to the same number:

  • More than six messages to the same destination number within an hour with the same sender or text may be blocked.
  • Users may not receive more than a total of 200 SMS per day across all incoming streams.


Unicode is supported.

Concatenated SMS

Concatenated SMS is supported.

Delivery Receipts

  • Transactional/OTP Traffic: DLR is supported and its reliable delivery receipts.
  • Promotional Traffic: DLR is not supported, nor its unreliable Network DR.

Traffic Restriction by Political Reason

Messages towards Jammu and Kashmir networks (for example, 405/55 - Airtel J&K) will be blocked by the government due to political sensitivity.

Political SMS is prohibited throughout the country during an election period.

Additional Information

For more information, see the following articles:

Was this article helpful?
11 out of 14 found this helpful
Have more questions? Submit a request