# E12017 — SMSSenderReserved

This sender identity is reserved and cannot be used as a sender.

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

## What to do

Choose a different sender; this identity is reserved and cannot be used.

## Related

- [E12xxx — SMS sending & delivery](/docs/api/errors/E12xxx): 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`