Resend event: email.failed, the send itself broke, fix the cause

TL;DR

For "email.failed": upgrade or wait; do not just retry in a loop. - API key problem: the key is revoked or lacks permission.

email.failed

Steps

1. Read the failure detail on the event and sort by cause:

   • Invalid recipient: fix or drop the address, check your validation.
   • Domain verification issue: the sending domain is not verified or lost verification. Re-check DNS (SPF, DKIM) in the Resend dashboard.
   • Quota limit: you hit your plan's sending limit. Upgrade or wait; do not just retry in a loop.
   • API key problem: the key is revoked or lacks permission. Rotate and redeploy.
2. Alert your ops channel. Unlike bounces, a failed event usually means many sends are failing at once.
3. Retry only after the cause is fixed, and only the messages that failed for a fixable reason.

When to use

You are seeing this: The email failed to send due to an error. Use this skill when you run into "Resend event: email.failed, the send itself broke, fix the cause".

When not to use

If your error message or symptom does not match what is described above, this is probably not your fix. Search for your exact error text instead of forcing this one to fit.

Versions

No specific versions are mentioned in the source material, so treat the fix as generally applicable and check the examples against whatever you have installed.

Why this happens

The original report does not dig into a root cause. It documents the symptom and the fix that resolved it.

Resend's event reference says email.failed occurs whenever the email failed to send due to an error, triggered by issues such as invalid recipients, API key problems, domain verification issues, email quota limits, or other sending failures. Verified live at https://resend.com/docs/webhooks/event-types.