> ## Documentation Index > Fetch the complete documentation index at: https://docs.orbit.devotel.io/llms.txt > Use this file to discover all available pages before exploring further. # Troubleshoot strict sender-ID mode rejects (SENDER_INVALID_FOR_DESTINATION) > Decode every strict-mode rejection code Orbit returns on an alphanumeric sender — wrong_length_exact, restricted_prefix, leading_trailing_space, and the alpha-unsupported destinations — and fix or roll back in minutes. # Troubleshoot strict sender-ID mode rejects Strict sender-ID mode re-checks every outbound alphanumeric sender against the destination country's format, prefix, and length rules **before the send is submitted** and rejects a violation with `422 SENDER_INVALID_FOR_DESTINATION`. This page decodes every rule code the rejection can carry and shows the fix for each — read the code out of the error's `details.rule` field before retrying, because a blind retry re-burns the same code. ## Gate the control The mode is an **opt-in, tenant-owned toggle** — it lives on the `sms_sender_id_strict` key in your organization's settings and defaults to off (permissive). Flip it via the dashboard sender-ID settings or through support. Turning it on re-applies the full destination-country rule set pre-send, so sends that used to pass with an advisory now fail closed. That is the behavior you asked for — the page decodes which rule fired. ## Decode the rule code A strict-mode rejection carries the violating rule in `details.rule`, the destination country in `details.country`, the offending sender in `details.sender`, and — for prefix violations — the matched prefix in `details.matchedPrefix`. | Rule code | Why it fired | Fix | | --------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | ---------------------------------------------------------------------------------------- | | `wrong_length_exact` | The country's hard length rule requires an exact character count — India (TRAI DLT) mandates **exactly 6 letters** | Set the sender to the exact length (6 chars for IN), e.g. `MYBANK` instead of `MYBANK12` | | `restricted_prefix` | The sender starts with a government/bank reserved prefix — Turkey (BTK) blocks `GOV`, `BANK`, `SGK`, `MEB`; KSA blocks `GOV`, `MOH`, `STC`; UAE blocks `GOV`, `TRA`; India blocks `UIDAI`, `SBI` | Rename the sender to drop the reserved prefix; `details.matchedPrefix` names it | | `leading_trailing_space` | The sender starts or ends with a space — carriers reject boundary whitespace | Trim the sender; internal spaces are fine (`MY BRAND`) | | `alpha_unsupported_country` | The destination's carriers do not support alphanumeric senders at all | Send from a phone number or short code for that destination | Other codes in the format family — `too_long`, `too_short`, `invalid_chars`, `wrong_alpha_only`, `wrong_numeric_only` — follow the same pattern: the rejection names the country and the sender, so adjust the sender value on the failing send path. SMS is billed when it is **submitted to the network**, not on delivery, and a carrier reject is not refunded. In permissive mode the same violating send is accepted and the wallet is charged — the pre-send 422 exists to stop that spend. ## Incoming state: mode off vs mode on | | Permissive (default) | Strict (opted in) | | ------------------------------------- | ------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------- | | Conforming sender | Accepted, no advisory | Accepted | | Format/prefix/length violation | Accepted; a `sender_deliverability_advisory` rides on the message metadata (`sender_format_nonconforming`, warning) | `422 SENDER_INVALID_FOR_DESTINATION` with `details.rule` | | Alpha-unsupported destination (US/CA) | Accepted; critical advisory `alpha_undeliverable_us_ca` | `400 VALIDATION_ERROR` — alphanumeric senders are not supported for US/Canada; use a phone number | | Alpha-unsupported destination (other) | Accepted; warning advisory `alpha_unsupported_country` | `400` validation error — use a phone number | Permissive advisories are informational only; strict mode blocks before any wallet deduction. ## Revert the mode Disable the mode the same way you enabled it — clear the `sms_sender_id_strict` key on your organization settings (dashboard sender-ID settings, or support). Permissive behavior resumes immediately: non-conforming sends are accepted again and violations return as advisory metadata. There is no migration or cooldown. ## Reproduce and fix each code A violating request in strict mode hits the 422 on the same endpoint you sent to. The examples below assume strict mode is on. ### `wrong_length_exact` — an 8-character sender to India ```bash theme={null} curl -X POST https://api.orbit.devotel.io/api/v1/messages/sms \ -H "Authorization: Bearer $ORBIT_API_KEY" \ -H "Content-Type: application/json" \ -d '{ "to": "+919876543210", "from": "MYBRAND1", "body": "Your order shipped" }' ``` ```json theme={null} { "error": { "code": "SENDER_INVALID_FOR_DESTINATION", "status": 422, "message": "Sender ID 'MYBRAND1' must be exactly 6 characters for India (TRAI DLT).", "details": { "country": "IN", "sender": "MYBRAND1", "rule": "wrong_length_exact" } } } ``` Fix: set `from` to a 6-character alphabetic header, for example `MYBRND`, or route the destination through a sender pool whose members conform — see [sender pools](/guides/sender-pools). ### `restricted_prefix` — a `BANK*` sender to Turkey ```bash theme={null} curl -X POST https://api.orbit.devotel.io/api/v1/messages/sms \ -H "Authorization: Bearer $ORBIT_API_KEY" \ -H "Content-Type: application/json" \ -d '{ "to": "+905551234567", "from": "BANKNOW", "body": "Your order shipped" }' ``` ```json theme={null} { "error": { "code": "SENDER_INVALID_FOR_DESTINATION", "status": 422, "message": "Sender ID 'BANKNOW' starts with a restricted prefix for Turkey (BTK).", "details": { "country": "TR", "sender": "BANKNOW", "rule": "restricted_prefix", "matchedPrefix": "BANK" } } } ``` Fix: rename the sender to drop the reserved prefix (`NOWBANK` passes; the check matches the **start** of the sender). If the brand genuinely needs the prefix, register it through the country's regulator channel — see [sender-ID registration](/compliance/sender-id-registration). ### `leading_trailing_space` — whitespace at the boundary ```json theme={null} { "error": { "code": "SENDER_INVALID_FOR_DESTINATION", "status": 422, "message": "Sender ID 'MYBRAND ' has leading or trailing whitespace.", "details": { "country": "DE", "sender": "MYBRAND ", "rule": "leading_trailing_space" } } } ``` Fix: trim the sender before sending — internal spaces are fine, boundary spaces are not. ### Alpha-unsupported destination For US/Canada recipients, strict mode raises a `400` instead: ```json theme={null} { "error": { "code": "VALIDATION_ERROR", "status": 400, "message": "Alphanumeric sender IDs are not supported for US/Canada destinations. Use a phone number instead." } } ``` Fix: send US/CA traffic from a phone number or short code; the implicit fallback without strict mode swaps to a platform number, but explicit is safer — see [sender resolution](/concepts/sender-resolution). ## Lens+: this is a tenant-owned control Like suppression and opt-out gating, the sender-ID rule set is a control **you own** — Orbit does not mandate it (see [Compliance posture FAQ](/compliance/posture-faq)). Enabling strict mode trades a permissive accept against a pre-send reject; disabling it trades back. Neither choice changes what carriers enforce — it only moves the reject from the carrier's DLR back to your API response. ## Related references * [Sender-ID Registration](/compliance/sender-id-registration) — register a sender per country so registration gates also pass. * [Sender resolution](/concepts/sender-resolution) — the full precedence chain from request selector to fallback. * [Sender pools](/guides/sender-pools) — route destinations through pools whose members conform per country. * [Error codes](/reference/error-codes) — the full send-path error table. * [Compliance posture FAQ](/compliance/posture-faq) — the map of every tenant-owned toggle.