Deliverability fundamentals for agent-sent email
SPF, DKIM, DMARC, warm-up, and frequency control — the guardrails that keep automated and agent-driven sends in the inbox.
Letting an agent send email raises the stakes on deliverability. A misconfigured automation can torch your sending reputation in hours. The fundamentals haven't changed — authentication, reputation, and engagement — but the guardrails matter more when a non-human is pulling the trigger.
This guide is a practical checklist for keeping automated and agent-driven email in the inbox.
Authenticate everything
SPF, DKIM, and DMARC are non-negotiable. Mailbox providers increasingly require them, especially for bulk senders. Most modern ESPs set these up for you on a verified domain — Brew includes DKIM, SPF, and DMARC on a custom sending domain even on its free plan; Resend and SendGrid walk you through domain verification.
- Verify your sending domain and publish SPF, DKIM, and DMARC records.
- Use a subdomain for marketing sends to insulate your primary domain.
- Monitor DMARC reports for spoofing and misconfiguration.
Warm up and protect reputation
Reputation is earned by sending wanted mail consistently. Ramp volume gradually on new domains/IPs, and keep engagement high by sending to people who actually want your email. An agent should never blast a cold full list — that's the fastest way to the spam folder.
- Ramp volume gradually; don't spike a new domain.
- Send to engaged segments; sunset chronically unengaged contacts.
- Honor unsubscribes instantly and keep one-click unsubscribe enabled.
Guardrails for automation and agents
When an agent can trigger sends, add hard limits it cannot exceed: frequency caps per recipient, daily send ceilings, and a required approval step for any send to a real audience. Test against a seed list first. Treat the agent's send permission as least-privilege and revocable.
- Per-recipient frequency caps and global daily ceilings.
- Seed-list testing before full-audience sends.
- Human approval gate on first sends; full action logging.
Frequently asked questions
- Do agent-sent emails need different authentication?
- No — the same SPF, DKIM, and DMARC apply. What changes is the need for stricter operational guardrails (frequency caps, approval gates) because a non-human is triggering sends.
- How do I stop an agent from hurting my reputation?
- Start read-only, require human approval for real-audience sends, cap frequency and volume, test against seed lists, and log every action so you can audit and roll back.
Tools referenced
Sources & further reading
Keep exploring: read the State of AI Email report or browse the tools directory.