You got **Invalid email parameter**. One field in the send was rejected (`from`, `to`, `subject`, or headers). This is a permanent reject for that attempt — fix the value, then send again.

## What to change

1. Open the campaign, workflow email, or transactional payload from the notification.
2. Check, in order:
   - **From** — must be `name@your-verified-domain`. No shared/test domain if that identity is gone. No spaces, angle-bracket typos, or unquoted display names that break the address.
   - **To** — a real mailbox. Role accounts are fine; empty/malformed addresses are not.
   - **Subject** — present. Extreme header injection (raw newlines) will fail.
   - **Reply-To / custom headers** — valid emails only.
3. If the From domain is unverified, [verify it](/docs/deliverability/how-to-verify-sending-domain) first.
4. Retry the send. Do not keep retrying the same broken From.

## Related

- [How to fix a failed send](/docs/deliverability/how-to-fix-email-send-failure)
- [Send Email API](/docs/api-reference/api-emails-send)