# E04059 — EmailTemplateVariableUnknown

The content references a `bird.` value we do not provide.

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

## What to do

Values under `bird.` are ones we fill in for each recipient. `bird.contact.<attribute>` reads a built-in contact field or one of the workspace's contact properties, so check the attribute is registered and spelled the same way. Everything else in a template is a parameter, written as a single word without the `bird.` prefix.

## 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`

## Related resources

- [Should I use a Bird SDK or call the API directly?](/explained/platform/should-i-use-an-sdk-or-call-the-api-directly) (answer)
- [Build your first integration](/learn/paths/integration) (course)
- [Send your first email](/docs/get-started/send-your-first-email) (docs)

[Get an implementation brief](/learn/workspace?topic=api-basics)