Errors

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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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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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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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missing_api_key

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

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invalid_api_key

• Status: 403
• Message: The API key is not valid.
• Suggested action: Generate a new API key in the dashboard.

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invalid_from_address

• Status: 403
• Message: The from address is not valid.
• Suggested action: Review your existing domains in the dashboard.

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invalid_to_address

• Status: 403
• Message: You can only send testing emails to your own email address.
• Suggested action: In order to send emails to any external address, you need to add a domain and use that as the from address instead of onboarding@resend.dev.

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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: This endpoint does not support the specified HTTP method.
• Suggested action: Change the HTTP method to follow the documentation for the endpoint.

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invalid_scope

• Status: 422
• Message: This endpoint does not support the specified scope.
• Suggested action: Change the scope to follow the documentation for the endpoint.

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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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daily_quota_exceeded

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

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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.