# E04066 — EmailTemplateVariableUnfillable

The template's published version reads a value nothing can fill.

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

## What to do

A template value is either a platform value under `bird.` or a single-word parameter the send supplies. This version reads one that is neither, so no request can put a value behind it. Rewrite the token in the draft and publish the template again, then send.

## Related

- [E04xxx — Email sending & delivery](/docs/api/errors/E04xxx): 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`