## Warm up a new sending domain
1. Verify the domain fully (SPF, DKIM, DMARC) before day one. Warm-up volume on an unverified domain is wasted effort and risky. Docs: https://resend.com/docs/knowledge-base/warming-up
2. Follow the new-domain ramp: day 1 up to 150 mails, day 2 up to 250, day 3 up to 400, day 4 up to 700 (50 per hour max), day 5 up to 1000 (75 per hour max), day 6 up to 1500 (100 per hour max), day 7 up to 2000 (150 per hour max). These are ceilings, not targets.
3. Send your most engaged mail first: transactional receipts, active-user notifications. Early positive engagement builds the reputation that later bulk mail rides on.
4. Never spike volume mid-ramp. A sudden 10x jump looks like a compromised account to inbox providers and triggers greylisting and throttling.
5. Watch the two guardrail metrics daily: bounce rate must stay under 4% and spam complaint rate under 0.08%. If either climbs, slow the ramp and investigate the list before increasing volume again.
6. Keep the cadence consistent. Warm-up is about establishing a pattern; erratic send days followed by silence resets the trust you built.
7. If you move to a dedicated IP later, that IP needs its own warm-up even on an established domain. Resend runs an automatic IP warm-up process, but the domain ramp discipline still applies.
8. Confirm the ramp worked by checking domain reputation signals in your dashboard and your seed inboxes before the first full-volume campaign.