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Error schema

We use standard HTTP response codes for success and failure notifications, and our errors are further classified by type.

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invalid_idempotency_key

  • Status: 400
  • Message: The key must be between 1-256 chars.
  • Suggested action: Retry with a valid idempotency key.

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validation_error

  • Status: 400
  • Message: We found an error with one or more fields in the request.
  • Suggested action: The message will contain more details about what field and error were found.

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missing_api_key

  • Status: 401
  • Message: Missing API key in the authorization header.
  • Suggested action: Include the following header in the request: Authorization: Bearer YOUR_API_KEY.

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restricted_api_key

  • Status: 401
  • Message: This API key is restricted to only send emails.
  • Suggested action: Make sure the API key has Full access to perform actions other than sending emails.

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invalid_api_key

  • Status: 403
  • Message: API key is invalid.
  • Suggested action: Make sure the API key is correct or generate a new API key in the dashboard.

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validation_error

  • Status: 403
  • Message: You can only send testing emails to your own email address (youremail@domain.com).
  • Suggested action: In Resend’s Domain page, add and verify a domain for which you have DNS access. This allows you to send emails to addresses beyond your own.

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not_found

  • Status: 404
  • Message: The requested endpoint does not exist.
  • Suggested action: Change your request URL to match a valid API endpoint.

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method_not_allowed

  • Status: 405
  • Message: Method is not allowed for the requested path.
  • Suggested action: Change your API endpoint to use a valid method.

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invalid_idempotent_request

  • Status: 409
  • Message: Same idempotency key used with a different request payload.
  • Suggested action: Change your idempotency key or payload.

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concurrent_idempotent_requests

  • Status: 409
  • Message: Same idempotency key used while original request is still in progress.
  • Suggested action: Try the request again later.

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invalid_attachment

  • Status: 422
  • Message: Attachment must have either a content or path.
  • Suggested action: Attachments must either have a content (strings, Buffer, or Stream contents) or path to a remote resource (better for larger attachments).

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invalid_from_address

  • Status: 422
  • Message: Invalid from field.
  • Suggested action: Make sure the from field is a valid. The email address needs to follow the email@example.com or Name <email@example.com> format.

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invalid_access

  • Status: 422
  • Message: Access must be “full_access” | “sending_access”.
  • Suggested action: Make sure the API key has necessary permissions.

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invalid_parameter

  • Status: 422
  • Message: The parameter must be a valid UUID.
  • Suggested action: Check the value and make sure it’s valid.

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invalid_region

  • Status: 422
  • Message: Region must be “us-east-1” | “eu-west-1” | “sa-east-1”.
  • Suggested action: Make sure the correct region is selected.

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missing_required_field

  • Status: 422
  • Message: The request body is missing one or more required fields.
  • Suggested action: Check the error message to see the list of missing fields.

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daily_quota_exceeded

  • Status: 429
  • Message: You have reached your daily email sending quota.
  • Suggested action: Upgrade your plan to remove the daily quota limit or wait until 24 hours have passed to continue sending.

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rate_limit_exceeded

  • Status: 429
  • Message: Too many requests. Please limit the number of requests per second. Or contact support to increase rate limit.
  • Suggested action: You should read the response headers and reduce the rate at which you request the API. This can be done by introducing a queue mechanism or reducing the number of concurrent requests per second. If you have specific requirements, contact support to request a rate increase.

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security_error

  • Status: 451
  • Message: We may have found a security issue with the request.
  • Suggested action: The message will contain more details. Contact support for more information.

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application_error

  • Status: 500
  • Message: An unexpected error occurred.
  • Suggested action: Try the request again later. If the error does not resolve, check our status page for service updates.

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internal_server_error

  • Status: 500
  • Message: An unexpected error occurred.
  • Suggested action: Try the request again later. If the error does not resolve, check our status page for service updates.