# E11009 — IPPoolUnknownForSend

Unknown IP pool.

- **HTTP status**: `422`
- **Type**: `validation_error`
- **Name**: `IPPoolUnknownForSend`

## What to do

List your IP pools for a valid pool reference, then retry the send.

Operations that resolve this:

- [Send a message](/docs/api/reference/create-email-message)

## Related

- [E11xxx — IP pools & dedicated IPs](/docs/api/errors/E11xxx): every code in this range
- [Errors](/docs/api/errors): the full wire contract, status mapping, and error catalog
- [Error handling](/docs/guides/errors): branching on `type` and `code`, validation details, and `vendor_code`