SMS Senders
The phone numbers and Sender IDs your SMS messages originate from.
SMS needs an origination identity the way email needs a verified domain. Start with the sandbox sender: it works immediately but only delivers to verified test numbers (a carrier rule for unverified senders). For production, New sender asks which countries you'll text and lists what each one needs: a US toll-free or 10-digit local number for US recipients, a Canadian local number for Canadian recipients, or an alphanumeric Sender ID for everywhere else. All of them need a brand first — see SMS Brands. Requesting a number or a Sender ID needs a paid plan. New to the channel? Start with SMS vs email.
Each number also carries a use case: what you send and how people opt in. Carriers read it to decide whether to approve the number, so it is submitted with the request and shown under the number afterwards. If you already have a number, the next one can reuse those answers instead of retyping them.
A sender moves through registration and verification states before it's active, and its status is re-checked at send time — a suspended or released number can't silently keep sending. The monthly number lease and the one-time carrier fees are quoted before you confirm, then taken from the sending wallet. See Wallet.
Where a number can send
Every sending identity has a reach: the countries it can deliver to. It is a carrier rule, not a setting, and it depends on the kind of identity. Unitpost shows it as a flag next to every number (hover it for the list) and states it in the New number menu and both wizards before you pay for anything.
- Toll-free number — US only. International sends from a toll-free number are routed best-effort through a shared identity, losing your brand and with no delivery guarantee; Unitpost does not forward them.
- 10-digit local (10DLC) number — US only, by carrier rule.
- Canadian local number — Canada only. A 10-digit number issued in Canada (a long code), requested by picking Canada in New sender: no brand or campaign registration, active within minutes, a small monthly fee. A US toll-free number never reaches Canada, so sending to both countries takes both numbers. Replies (STOP, ARRET, HELP) come back to Unitpost like a 10DLC number's do.
- Sandbox — US only, and only to your verified test destinations.
- Alphanumeric Sender ID — the country it is enabled for. Enable one Sender ID per country; US, Canada and China do not support Sender IDs at all.
- Short codes and other countries' long codes — the country they are issued in. Not available in Unitpost yet.
Sender IDs — your name instead of a number
An alphanumeric Sender ID is a name of up to 11 letters, digits or hyphens (at least one letter; no leading or trailing hyphen) that appears on the recipient's phone instead of a number — "Acme" rather than +44… . Sender IDs are free: there is no purchase and no monthly fee. Each brand has one Sender ID string (derived from the brand name; change it on the brand), and you enable it per destination country by picking those countries in New sender (or Add countries on the Sender ID). Each enabled country appears as its own row in the numbers table with the country flag.
- Instant countries (most of Europe, Latin America, Asia-Pacific and Africa): the Sender ID is requested directly and is active within a minute.
- Registration-required countries (for example the United Kingdom, Finland, Spain, Singapore, Belarus, Kazakhstan): the regulator reviews a registration first. It is composed from your brand and use case; a few countries ask for one or two extra answers — Spain's alias holder details — and only those are asked. Singapore's letter of authorization comes from the brand's company documents. Approval takes days to weeks; the row shows the regulator's status and, if it comes back, what to fix and a Resubmit button.
- Countries whose registration needs company documents (for example the UAE, Ireland, Saudi Arabia, Turkey, Vietnam, the Philippines, Indonesia) are unlockable: the dialog shows which documents each one needs, and the moment your brand holds them the country becomes requestable. Missing ones are named — "needs: registration certificate" — with a link to the brand's Company documents section. Documents are sent to that country's registry as part of the registration, and a correction request about a document shows on the Sender ID with a Replace link. India needs a separate DLT registration and is not available.
Unregistered Sender IDs get rewritten
In a country that requires registration, an unregistered Sender ID is replaced by the carrier with "NOTICE" ("LIKELY-SCAM" in Singapore and Ireland) and the message may not be received. Unitpost therefore never sends from a Sender ID in such a country until its registration is approved — the sender stays pending until then.
Sender IDs are one-way
Recipients can't reply to a Sender ID, so there is no STOP by text. Marketing sent from a Sender ID must still be opt-out-able: include a link to the hosted preference page in the message, or record opt-outs through POST /v1/contacts/{id}/sms-consent. Consent rules are unchanged — marketing needs express consent on record regardless of the identity.
Out-of-reach recipients are skipped, not attempted
A message to a recipient outside the sender's reach is not sent: it lands as suppressed with the reason ("This number sends to US recipients only") and is never billed. The country comes from the phone number itself — a Canadian or Caribbean +1 number is labelled CA or its island, not US. Campaigns tell you how many recipients this affects before you send, and the public API returns each number's reach (GET /v1/sms/numbers → reach).
Keep marketing and OTP apart
Carriers degrade deliverability for numbers that mix bulk marketing with time-sensitive transactional traffic. When you start sending campaigns, add a dedicated marketing sender so a blast can never slow your verification codes.