You configure your sender as your brand name, test it, and it arrives perfectly. Then a customer in another country gets the same message from a random five-digit number, and someone in a third country never gets it at all. Sender ID rules are why.
What a sender ID actually is
The sender ID is what appears in the from field on the handset. There are three kinds and they behave completely differently.
- Alphanumeric. Your brand name, typically up to eleven characters. Looks professional. Cannot be replied to.
- Numeric long code. A standard phone number. Can receive replies, which matters for two-way messaging.
- Short code. A five or six digit number, usually leased and market-specific.
The four regimes you will run into
Countries fall into roughly four groups, and knowing which one you are sending into explains almost every delivery surprise.
- Alphanumeric allowed, no registration. Much of Europe historically operated this way. You set a brand name and it arrives. Simple, and gradually becoming rarer.
- Alphanumeric allowed, registration required. The direction of travel almost everywhere. You must pre-register the sender ID before it will deliver. India runs DLT registration; several Middle Eastern and African markets have equivalents.
- Alphanumeric not permitted. The US and Canada. Messages must come from a registered number, which is what the 10DLC framework exists to manage.
- Dynamic replacement. Some carriers silently overwrite whatever you send with their own number. Your message arrives, your branding does not.
Why this breaks quietly
The failure mode is what makes this expensive. Sender ID problems rarely produce a clean error. The gateway accepts your message, the API returns success, and the message is either rewritten or dropped at the carrier. Your WordPress logs look perfect.
The tell is geography. If delivery is fine in one country and poor in another, stop debugging your configuration and check sender ID rules for the destination. Our gateway troubleshooting guide covers the wider diagnostic sequence.
Practical rules that hold everywhere
- Keep it under eleven characters and avoid spaces and punctuation. Longer IDs get truncated unpredictably.
- Register early. Sender ID approval can take days or weeks depending on the market. It is the item most likely to delay a launch, so start it before you build the integration.
- Do not use alphanumeric for anything needing a reply. Customers will try to reply and their message goes nowhere, which reads as being ignored.
- Use a consistent ID per market. Rotating sender IDs looks like spam to filters and confuses customers who have saved your number.
- Test per country, on a real handset on the actual network, before you launch there.
Choosing a gateway with this in mind
Providers differ enormously in how well they handle regional registration. A gateway with direct local relationships will usually manage sender ID approval for you in its strong markets, while a global reseller may leave you to work it out. If you sell into a specific region, that is a strong argument for a regional provider such as MSG91 for India or Termii for African markets, rather than forcing one global account to cover everything.
Compare the options in the supported gateways list.
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