A sent email cannot be taken back

Every other Resend call can be run again. send-email and send-batch-emails put mail in someone's inbox, and nothing undoes that. Treat the send as the last step of a short checklist.

1. Check the sending domain

The from address must be on a domain the account has verified for sending. Run list-domains and find the domain of the from address:

• verified: send.
• pending, not_started, failed, or partly verified: do not send. Run get-domain and show the user the DNS records that are not verified yet.
• Not in the list: the account cannot send from it. Ask which verified domain to use. Do not pick one for the user.

onboarding@resend.dev sends without a domain, but only to the account owner's own address. It is for a first test, not for real recipients.

2. Prove it on a test address first

Before a real recipient, send the same message to Resend's test addresses. Remove cc and bcc, and put only test addresses in to. A real address in any recipient field gets the test email before the user confirms in step 3.

• delivered@resend.dev: delivered. Add a label for each case, for example delivered+welcome@resend.dev.
• bounced@resend.dev: a hard bounce.
• complained@resend.dev: delivered, then marked as spam.
• suppressed@resend.dev: suppressed as an address that bounced before.

Then run get-email on the result. Its status is the truth: sent means Resend accepted the message, delivered means the receiving server accepted it.

3. Confirm before a real inbox

Show the user the from, to, cc, bcc, subject, and body, and wait for a clear yes. Get this confirmation every time. Approval for an earlier send does not cover this one.