API errors
Email API errors, and how to fix them.
What an email provider’s error means, why it happened and the code that fixes it, checked against the provider’s own documentation. Each page ends with what SendRaven, an email API for AI agents, does in the same situation.
Resend
429 rate_limit_exceededResend returns 429 above 10 requests a second per team.Checked 28 September 2026.429 daily_quota_exceededResend returns 429 once a Free plan sends 100 emails in a UTC day, received mail included.Checked 28 September 2026.403 validation_errorResend returns 403 because resend.dev only delivers to your own address.Checked 28 September 2026.
SendRaven’s own errors
Every SendRaven error is { error: { type, message } }, a type means the same thing on every endpoint, and the errors reference says for each one whether to retry, fix the request or stop and tell a person.