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SMS sender ID in Sri Lanka: what a mask is and how to register one
A sender ID, also called a mask, is the name customers see instead of a phone number when a business sends them an SMS. In Sri Lanka, the major mobile networks expect alphanumeric sender IDs to be registered before you send.
The short answer
Register an alphanumeric sender ID that matches your brand before your first send. Several international SMS providers report that Sri Lankan networks block or overwrite unregistered sender IDs.
On Unecast, registration typically takes 1 to 2 business days once your documents are complete, subject to operator approval. Other providers report from a few working days to about three weeks, depending on the route. Keep each sender ID to one kind of traffic, such as OTPs or promotions. Put your brand name in every message.
On Unecast, you request the sender ID in the SMS portal. It shows as Pending while we register it, then Active. Only active sender IDs can send.
What a sender ID (mask) is
A sender ID is the name that appears in the "from" line of an SMS. A bank might send codes as its short brand name rather than from a mobile number. In Sri Lanka the term "mask" is common. Dialog's own eSMS page says messages are delivered "under a user ID (Masking) instead of a mobile number" (Dialog Business, eSMS, checked 6 November 2026).
A recognisable sender ID tells customers who is writing. It also helps them spot fake messages that use a different name.
Alphanumeric vs numeric sender IDs
An alphanumeric sender ID uses letters and numbers, such as a brand name. AWS and Sinch both state a length of 3 to 11 characters for Sri Lanka. A numeric sender ID is a phone number or short code.
| Type | What providers report for Sri Lanka |
|---|---|
| Alphanumeric (registered) | Supported on all major networks (LINK Mobility, Vonage, Sinch). Registered IDs are preserved (Twilio). |
| Alphanumeric (unregistered) | Rejected, blocked or overwritten (Telnyx, Sinch). Twilio and Vonage name Dialog and Hutch. |
| Numeric (phone number) | Overwritten on Dialog (Vonage, LINK Mobility). Twilio reports numeric sender IDs to Dialog, Etisalat and Hutchison are blocked from 29 July 2026. |
Sources: Twilio, Vonage, LINK Mobility (updated 30 April 2026), Sinch, Telnyx, AWS, all checked 6 November 2026.
For business messaging, a registered alphanumeric sender ID is the dependable choice. Infobip reports that domestic traffic can use a numeric sender.
Sri Lanka's mobile networks today
Provider guidelines still use older network names. As of 6 November 2026, the market has three main network operators: Dialog Axiata, SLT-Mobitel and Hutch (OperatorWatch, 4 June 2026).
| Network today | Older names in guidelines | Sender ID notes |
|---|---|---|
| Dialog Axiata | Dialog, Axiata, Airtel. Airtel Lanka ceased as a company on 30 August 2024 after amalgamating with Dialog. The Airtel brand continues. | Registration required (Twilio, Vonage). Numeric senders overwritten (Vonage, LINK Mobility). |
| SLT-Mobitel | Mobitel, Sri Lanka Telecom | Allows only OTP and transactional traffic (Twilio, Telnyx). Twilio lists this under international registration. |
| Hutch | Hutchison, Etisalat. Hutch acquired Etisalat Lanka. | Registration required (Twilio, Vonage). Message must contain the brand name that matches the sender ID (reported by Vonage). |
Sources: Dialog Axiata, 30 August 2024; Mobile World Live and OperatorWatch on Hutch and Etisalat; provider pages above. Checked 6 November 2026.
Twilio states that "starting on July 29, 2026, messages with unregistered Sender IDs to these networks will be blocked" (Dialog, Etisalat and Hutchison). That date has passed, so treat registration as required.
What registration needs and how long it takes
Providers ask for broadly the same details. Telnyx, LINK Mobility, AWS and Sinch all request:
- The sender ID you want, and your company name and website.
- The use case or traffic type, such as OTP, notification or marketing.
- Sample messages that include your brand name.
- A business registration document (Telnyx, LINK Mobility).
- Proof of your right to the brand if the link to your company is not obvious (AWS, Telnyx).
AWS also asks for a signed letter of authorisation on company letterhead (reported by AWS). Each provider sets its own list. On Unecast, ask us for the current document list.
| Provider | Reported registration time |
|---|---|
| Unecast | Typically 1 to 2 business days once documents are complete, subject to operator approval |
| Sinch | About 4 working days |
| Infobip | About one week on average |
| Twilio | 3 weeks (domestic and international pre-registration) |
Sources: Sinch, Infobip, Twilio, checked 6 November 2026. Times are each provider's own estimate.
Incomplete details slow approval, as LINK Mobility notes. Start registration well before a launch date.
Content restrictions: transactional vs promotional
Transactional messages are ones the customer expects, such as OTPs, alerts and order updates. Promotional messages advertise offers or products. Networks treat the two differently.
- Mobitel limits use cases. Twilio says Mobitel "only allows OTP, OTT, and transactional traffic, such as banking and payment messages." Telnyx reports the same.
- No generic sender IDs. Names like INFO, SMS, Billing or Support are not allowed (Vonage, Sinch).
- Brand in every message. Sinch and AWS require the brand or company name in the content. Vonage reports this for Hutch.
- One use case per sender ID. AWS states that transactional and promotional content must use separate Sri Lanka sender IDs (reported by AWS).
- Consent for promotions. Twilio, Telnyx and Vonage all require opt-in consent before marketing messages.
Vonage also reports a ban on political, religious, gambling and unsolicited promotional content. Promotional SMS also carries a levy and consent rules. See our guide to bulk SMS rules in Sri Lanka.
To check how long a message is and how many SMS parts it needs, use the SMS character counter.
How sender IDs work on Unecast
Unecast runs SMS in a separate SMS portal. The steps below come from our bulk SMS gateway and SMS API pages.
Before you request one, test the name with our free SMS sender ID checker. It checks length, characters, phone-number lookalikes and generic names.
- Register in the SMS portal with your work email and company details, then confirm your email.
- Request your sender ID in the portal under Sender ID settings.
- It shows as Pending while we register it and submit it for approval.
- It then turns Active. A rejected request shows the reason.
- Send with it. Only active sender IDs can send.
In the REST API, put the active sender ID in the from field. Over SMPP, a name such as YOURBRAND uses source_addr_ton 5 (alphanumeric) and source_addr_npi 0. An invalid sender ID returns 0x0000000A (ESME_RINVSRCADR).
For OTPs, see OTP SMS. We do not publish a fixed document list or fee for sender IDs. Ask us for the current document list.
Frequently asked questions
What is a sender mask in Sri Lanka?
A sender mask is the name shown instead of a phone number when a business sends an SMS. It is the same thing as a sender ID. Most businesses use their brand name.
Do I need to register a sender ID to send SMS in Sri Lanka?
Yes, for alphanumeric sender IDs. Twilio and Vonage report that Dialog and Hutch require registration. Telnyx and Sinch say unregistered sender IDs are rejected or likely blocked.
How long does sender ID registration take in Sri Lanka?
On Unecast, sender ID registration typically takes 1 to 2 business days once your documents are complete, subject to operator approval. Other providers report about 4 working days (Sinch), about one week (Infobip) and 3 weeks (Twilio). Complete information shortens the process, so start registration before your launch date.
Can I use a phone number as the sender ID?
Not reliably. Vonage and LINK Mobility report that numeric senders are overwritten on Dialog. Twilio reports numeric sender IDs to Dialog and Hutch are blocked from 29 July 2026. Use a registered alphanumeric sender ID.
Can I use one sender ID for OTPs and promotions?
It is safer not to. AWS reports that Sri Lanka needs separate sender IDs for transactional and promotional content. Twilio and Telnyx report that Mobitel allows only OTP and transactional traffic.
When can I start sending on Unecast?
When your sender ID shows as Active in the SMS portal. It shows as Pending while we register it and submit it for approval. Only active sender IDs can send.
Keep reading
Get your sender ID ready for Sri Lanka
Tell us your brand and use case. We register your sender ID and submit it for approval before your first send.