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Dil notu

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Fix an empty sender pool (SENDER_POOL_EMPTY)

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Symptoms

• The send request returns HTTP 422 with code SENDER_POOL_EMPTY, and the response names the pool that was empty.
• The dashboard Delivery Log shows no row for the message — the send was rejected before queueing, so there is nothing to deliver.
• The pool’s detail page prompts you to add a DID, and the senders list for the pool is empty.

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The sender-pool state machine

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Causes

• The pool’s sender_dids list has no entries. Two ways a pool reaches that state: it never had members (created with an empty list and never filled, or the last member was removed), or the send carried a narrower recipient filter and none of the pool’s members were eligible, leaving zero candidates for that recipient.
• A messaging service, campaign, or sender routing rule still points at the pool, so every send routed through it fails with the same code.

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Pool membership mechanics

• E.164 DID — listed by GET /api/v1/numbers; check the inventory before attributing the empty-pool rejection to a missing row.
• Numeric short code or alphanumeric sender ID — set via the API (PATCH /api/v1/messaging/sender-pools/{id} with sender_dids); the dashboard’s pool editor carries them over when you edit there.

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The in-flight retry semantics

• The idempotency key survives the pool swap. The key scopes to the request, not to the pool id inside it — when you fix membership (or route through another pool) and resubmit the same key with the same body, Orbit returns the cached 422 instead of a second send.
• The body must be byte-identical. If your fix changes the body — for example a different sender_pool_id value — the same key resubmits to 409 IDEMPOTENCY_KEY_REUSED, not to a send. Generate a fresh key for the corrected request, or leave the key unset (neither the 422 nor the 409 consumes the rejection).
• Nothing wrote a cache entry to clean up. Because the rejection happens before queueing, the idempotency cache holds either nothing (the plain rejection) or the 422/409 itself — both expire on the key’s 24-hour window. There is no mid-batch selection state to unwind; the idempotency and safe retries concept page covers the key-vs-body binding in full.

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Gate it before launch: preview as a diagnostic

• Run GET /api/v1/messaging/sender-pools/{id}/preview?recipient=<E.164> on a synthetic recipient after provisioning or editing a pool; expect a sender, not the 422, before you wire the pool into a campaign or messaging service.
• Combine with GET /api/v1/numbers so the pre-launch check both resolves and owns its sender before traffic flows.
• When a recipient filter narrows the pool to zero candidates, preview the actual recipient you will send to — the failure mode is narrower than the empty list the pool row itself reports.

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Route elsewhere: pass a sender_pool_id, or repoint the wiring

• One-off divergence — pass a different sender_pool_id on the send request itself (generate a fresh idempotency key, per the retry semantics above). Use this when only certain traffic should route away.
• Wiring repoint — move the messaging service’s default pool, the campaign, or the routing rule to a non-empty pool when everything routed through the empty pool should move. Use this when the pool itself is being retired or reworked.

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Client hints: branch on the confirmed channel and sender

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Composite recovery

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Example envelope

curl -X POST https://api.orbit.devotel.io/api/v1/messages/sms \
  -H "X-API-Key: dv_live_sk_your_key_here" \
  -H "Content-Type: application/json" \
  -d '{
    "to": "+14155550100",
    "sender_pool_id": "pool_emptypool",
    "body": "Order shipped"
  }'

{
  "error": {
    "code": "SENDER_POOL_EMPTY",
    "status": 422,
    "message": "Sender pool pool_emptypool has no DIDs configured"
  }
}

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Related references

• Sender pools — create pools, add members, and understand selection strategies.
• Sender resolution — where the pool pick sits in the full precedence chain.
• Idempotency and safe retries — the key-vs-body binding semantics the retry section above applies.
• Troubleshoot sender resolution and pool errors — the three sibling codes (SENDER_REQUIRED, SENDER_POOL_NOT_FOUND, NO_SENDER_CONFIGURED).
• FAQ: Why did my send return 422 SENDER_POOL_EMPTY? — the one-line version of this page.
• Error codes — the full sender error table.