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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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 we 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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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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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_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@resend.com 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.