# SMS senders Every SMS sent through the A2P Messaging API goes out from a sender registered in your account. This page covers how a request identifies its sender, the 422 on an unregistered `from`, per-country registration with a legal profile, the exact spelling of a filed alias, and what is billed when a message is blocked. **Language:** en **Audience:** developer **TLDR:** Register your senders in the dashboard (SMS > Senders) and send from them: identify one by its id in `sender` (recommended) or by its name in `from`. A `from` that matches none of your senders returns 422 on `from`, and nothing is sent or charged. Where a country requires it, register the sender for that country with your legal profile, and send the alias exactly as filed, capitals included. Only wholesale providers who request the wildcard route can send an unregistered `from`. **Search keywords:** from field, sender id, sender name, unregistered sender, sender not found, 422 from, register sender, sender registration, legal profile, country registration, cnmc, alias spelling, exact alias, case sensitive sender, numeric sender, opt out substitution, unregisteredBypassRouteOptOut, blocked and charged, what is billed, fallback sender, wildcard sender **Related pages:** /a2p-messaging-api/channels/sms/wildcard-route, /a2p-messaging-api/channels/sms/destination-countries, /a2p-messaging-api/http/quickstart, /platform/en/channels/sms/coverage-and-delivery, /platform/en/channels/countries **Docs index (every page):** https://staging-instasent-docs-nextjs.oscar-284.workers.dev/llms.txt **This zone's index:** https://staging-instasent-docs-nextjs.oscar-284.workers.dev/a2p-messaging-api/llms-full.txt **This page:** https://staging-instasent-docs-nextjs.oscar-284.workers.dev/a2p-messaging-api/channels/sms/senders/ (HTML) · https://staging-instasent-docs-nextjs.oscar-284.workers.dev/a2p-messaging-api/channels/sms/senders.md (Markdown) The **sender** is the name or number the recipient sees as the origin of your SMS. In the A2P Messaging API it is not a free-text field: **every message goes out from a sender registered in your account**, the same senders you see in the dashboard under **SMS > Senders**. Registering them is what lets each message arrive under your brand, and in the countries that ask for it, what lets us file that brand with the regulator or the operators. The per-country rules — which countries accept any alphanumeric sender, which replace it with a number, which require a registration first — are the same for the dashboard and the API, and are documented once: - [Coverage & delivery](/platform/en/channels/sms/coverage-and-delivery) - What happens when you send to a country that requires registration and yours isn't approved yet. - [Countries](/platform/en/channels/countries) - Every destination, with what it asks for on each channel. ## Senders are required A request names its sender in one of two ways: - **`sender`** — the id of one of your senders. **This is the recommended form**: it is stable if the sender is renamed, and unambiguous. An id that doesn't exist returns `422`. - **`from`** — the sender's name: 3 to 11 characters when alphanumeric, 3 to 14 digits when numeric. It has to match one of your registered senders by name. When both are sent, `sender` wins, and the `from` in the response is the sender's canonical name. A `from` that matches none of your senders is **refused with `422`**, and **nothing is sent or charged**. The error is reported on the `from` field: ```json { "errors": { "fields": { "from": ["The sender is not registered in this project, register it before sending"] } } } ``` In a [bulk request](/a2p-messaging-api/http/bulk) the same check runs per item: a refused item is reported in `errors` and the rest are sent. > **Note**: The one exception is the [wildcard route](/a2p-messaging-api/channels/sms/wildcard-route), > for wholesale providers that carry third-party traffic under their own customers' sender > names. It is not available by default: it is requested from the SMS channel's **Settings** > tab in the dashboard. ## Register the sender in each country that requires it Creating the sender in your account is the first step. Countries with a regulator in force, such as Spain, also need an **accepted registration** of the sender for that country, which you request and follow in the **sender's sheet** with your company's legal profile. Which countries ask for it, how the sheet shows each one, and what happens while a registration is pending are in [SMS coverage](/a2p-messaging-api/channels/sms/coverage). ## Send the alias exactly as you filed it Where a sender is filed with a regulator, the check against that registry is **literal** — character by character, capitals included. Nothing is normalised on the way. If you filed **`PEDRO`** and your request carries **`Pedro`**, that check reads your alias as not filed, with all the consequences of not being filed — even though the procedure went through and was approved. It is worth a line in your integration, because it is the hardest failure to diagnose from the outside: the register shows as approved, the regulator has your alias, and the messages still don't arrive as they should. Sending by `sender` id avoids it; if you build `from` from a database field or a template, make sure it reproduces the filed spelling. ## Choosing blocking over substitution Some senders would rather not go out at all than go out with the recipient seeing a different sender — a brand where the name is the point, or traffic where an unexpected sender would raise a support case of its own. The sender carries a field for that: **`unregisteredBypassRouteOptOut`**. With it on, in a country whose regulator is in force, that sender never takes an alternative route — the block applies as it stands, and the message is reported as blocked by regulation. Two limits worth knowing before you set it: - **It changes nothing where there is no regulator**, and nothing before a regulator's rules take effect. It isn't a global "never substitute my sender" switch. - **It doesn't change what is billed** — see [What is billed](#what-is-billed). It lives on the sender, not on the account, on purpose: on an account with the wildcard route, the Wildcard Sender carries all of that account's unregistered traffic, so the choice belongs with the sender that carries it. ## What is billed **A message refused with `422` — for its sender or its [destination country](/a2p-messaging-api/channels/sms/destination-countries) — is not sent and not charged.** Once a message has been accepted, **a message blocked from a registered sender of your own is not billed**, while a blocked [transit message](/a2p-messaging-api/channels/sms/wildcard-route#what-is-billed) is. Delivery reports tell you the outcome per message — see [DLRs](/a2p-messaging-api/http/dlrs). --- This is one page of the Instasent documentation. For the complete machine-readable index of every guide and API reference, fetch https://staging-instasent-docs-nextjs.oscar-284.workers.dev/llms.txt — start there for full context.