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 who 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.

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. 

PE ID is mandatory to provide along with Header for successful sms termination.

Entities has 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 Feb 2021.

Template scrubbing:

Similar to the Sender ID upload process, you need to upload these templates with any one operator DLT portals. Brand Name is mandatory to be included in content for template registration with effect from Oct 11 2020.

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


Complying with DLT and Vonage

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

All customers finished DLT registration are required to notify Nexmo team 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 DLT portal template section) and saved as csv format with entityID as file name. <entityid.csv>

Please notice Vonage is not responsible for domestic entities registering for DLT. Also we does not verify if domestic entities have provided their PED, template ID and the sender ID correctly.

The carrier does, if a message errors due to these fields not being provided or valid, 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 PE ID (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 PE ID (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, customer will fall onto domestic promotional(SMS without opted in) category with restrictions as mentioned below.

If you are an Int'l customer or have different sms type 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 next day.

DLR not supported started since 9 Oct 2020

International (transactional/Opted-in Promo)

International originated transactional content & Opt-in Promo content.

(If client registered in India,but sms originated outside India, will be identified as International traffic). 

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

For OTP/Transactional traffic mainly. For Opted-in promo, content need whitelisting though AM prior to sending sms.


SMS Delivered 24/7 via International route.

No restrictions for NDNC listed numbers.

 For opted in promo sms, same Regulation apply as in  for Domestic Promotional(Opted in) listed below.

International Promotional (without opt-in) Promo/Marketing content Not supported

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

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

DLR not supported from 9 Oct 2020

Domestic Promotional (opted in) This traffic can only be routed via special promo binds with opted in confirmations from each subscriber MSISDN 6 digit Alpha with DLT pre-registration 10am-9pm delivery with NDNC restriction but with alpha SID support.
However, handling party (customer) of the promo content must have subscriber opted in consent per each MSISDN and should provide the information to the providers handling the traffic either upfront or on demand in an event if the termination party gets a complaint from a mobile operator (mobile subscriber complaining to operator for receiving a promo content) as proof the subscriber has given consent to receive promo content. Failing to do so (not defined the actual time period) provider will be liable for penalty charges depend on the number of violations. Please refer to Schedule IV, Article 10 --> for details. Need to have contractual provisions in order to accept the penalty charges in case of violation.



For enterprise that finished DLT application successfully, the SMS Sender ID will be resulted with additional prefix with 2 letters, depending on the number belongs to which final operator. 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 short code.


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 be able to 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 its 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 are prohibited during election period throughout the country.



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

Please get in touch with your account manager to discuss on 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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