Email Sender delivers transactional and outreach emails with proper threading, automatic unsubscribe handling, and idempotent delivery. Built for agents running email campaigns that need reliable, compliant, thread-correct sending.
It handles RFC 5322 threading headers so replies land in the right conversation in any email client. One-click unsubscribe links are signed and included automatically. Idempotency is built in — if the same campaign/lead/stage combination is sent twice, the second call is silently skipped. Unsubscribed recipients are blocked on every send attempt.
What you can do
- send_email — send an email with proper threading, an automatic unsubscribe link, and idempotent delivery
- list_thread — retrieve the full conversation history for a lead by campaign and lead ID
Who it's for
Sales teams, growth agents, and developers running automated outreach campaigns where deliverability, threading, and compliance matter. Ideal for multi-step follow-up sequences where you need a clean record of what was sent.
How to use it
- Call send_email with the recipient, sender, subject, and body in markdown. Include a campaign_id, lead_id, and stage for idempotency.
- For follow-up emails in the same thread, pass the original message's ID as in_reply_to and all prior message IDs as references.
- Use list_thread to check the conversation history for a lead before deciding whether to send another step.
Getting started
Connect your Resend account by saving your API key, then call send_email with your first outreach message.
