India: SMS Features & Restrictions

Vonage supports Domestic and International enterprises SMS business to India.

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

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 the end recipient via domestic connections.

Please notice International Enterprises are not affected by this change.

Timeline information of the DLT implementation:

Phase-1: Lived on 1st June 2020. SenderID/Header Scrubbing.

Only DLT registered SenderIDs able to terminate SMS on domestic routes.

Entity Registration and Header Registration was mandatory.

Phase-2: Lived on 19th Nov 2020. PEID/Entity Unique ID Scrubbing.

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 got their entities registered.

Phase-3: Live on 1st April 2021. Template/Content Scrubbing.

Only DLT registered Templates, along with SenderID & 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 with effect from Apr 22, 2021. Following points to note for successful SMS delivery

  • It is mandatory to have brand name in all category of messages from 22nd April 2021 onwards. 
  • Accordingly, changes should be made to your applications also.
  • The exact text should match from your application to suppliers to the DLT Platform.
  • Only Approved Templates should be submitted/uploaded to the Vonage.
  • Header Mapping against each template should be verified. Incase ‘X’ header 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 in the text should not exceed 30 characters. more than 30, please add more variables accordingly.
  • 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)

Other info on DLT

As per TRAI’s regulations of DLT, during 21:00hrs – 10:00 hrs IST are set to be blocked for SMS delivery for end recipients who registered with Do Not Disturb Service (DND).  In other words, promotional SMS can be delivered only between 10 hrs - 21 hrs IST.

Meanwhile, operators will stop supporting delivery notifications for messages sent via Promotional routes with Numeric headers. SMS delivery receipt for promotional traffic stopped support by operators since 9th Oct 2020.

This is a continuous endeavour to create a cleaner and transparent system in the Indian telecom industry and curb Unsolicited Commercial Communication (UCC) and an enhanced mobile subscriber policy. The new regulation can be accessed here

Vonage Error Codes for DLT related issues

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


Complying with DLT and Vonage

1. Resister your Principal Entity, Headers, Templates in DLT portal using any one url below

As per TRAI's new regulation, for SMS through domestic connections, all enterprise must register their Principal Entity, Headers, Templates with the Brand Name & provide consent on any one of the DLT systems below. -  (Vodafone-Idea Ltd DLT URL) -  (BSNL DLT URL) -  (Airtel DLT URL) - (Reliance JIO DLT URL)


2. Choose your approach on how to achieve regulatory compliance while submitting your messages to Vonage platform...

    Option 1 (Preferred): You make a change and submit DLT required parameters at every request

  • Make development changes at your end to maintain your Entity ID, Sender ID/Header and Templates as registered in DLT portal.
  • Use additional Parameters as mentioned below in the APIs/SMPP properties to submit your messages to Vonage.
  • Inform Vonage team with SenderID  to enable routing for option1.
  • Start Sending sms upon above setup confirmation.

   Option 2: You let Vonage detect your template with zero change at your end

  •  Make ready your DLT approved PEID, SenderID, Template csv file.
  • All customers who have completed DLT registration are required to notify the Vonage API Support team with the following DLT information by contacting
    • PEID- (Entity unique ID received from DLT after Entity registration Approved) :
    • Entity name - (Company name under which registered on DLT) :
    • Sender Name - (6 Alpha/Num Sender/Header which is registered in DLT and approved)
    • Registered on - (The DLT platform information) :
    • Template file  - (as downloaded from the DLT portal template section) and saved as CSV format with the entityID as the file name. <entityid.csv>

Please notice Vonage is not responsible for domestic entities registering for DLT. We do not verify if domestic entities have correctly provided their PEID, senderID and templateIDs.

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.

Vonage has added functionality within the 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)


SMS Types

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

If you are an Int'l customer or have different SMS type other than as listed below, please contact your acc manager or write to

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.  

The 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 started 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 



For enterprises that finished the DLT application successfully, the SMS Sender ID will be prefixed with an additional 2 letters, depending on the number belongs to which final operator. A full list of prefixes can be found here: India Pre-registered SenderID Prefixes

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


Do Not Call Registry(NDNC)

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


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 6 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.

Other features/restrictions: 


Unicode is supported.

Delivery Receipts:
Transactional/OTP Traffic: DLR is supported and its reliable delivery receipts.

Promotional Traffic: DLR is not supported. And/Or it's unreliable Network DR.

Traffic restriction by political reason:

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

Please also note that political SMS is prohibited during the election period throughout the country.



Please note that it is possible to also complete the registration of Alpha Sender IDs to other countries.

Please get in touch with your Account Manager to discuss processing Sender ID registration If you have more than 1 million messages a month.


Global SMS Features Overview (Outbound only)

Global SMS Numbers Features Overview


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