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How to Warm Up a Domain for Cold Email (Without Hurting Deliverability)

Warming up your inbox properly is key to avoiding spam folders. Here’s how to warm both new/existing domains using warming tools.

Meagan Glenn avatar
Written by Meagan Glenn
Updated over a month ago

Warm your existing domain and inboxes

Even if you’re already sending cold emails, warming your inboxes helps pad deliverability.

What to do:

  • Add your current inboxes to a warming tool like Smartlead

  • Set volume to ~10 emails/day

  • Set reply rate to 95–100% (most warmers simulate replies for this)

Campaign sending limits:

  • Keep total outbound volume to ~50 emails/day
    → That’s about 17 new people enrolled per day

  • This helps maintain a safe domain reputation while warming in the background


Warm a new domain (not a subdomain)

New domains should be warmed gradually before full use.

What to do:

  • Register a new domain

  • Add it to Smartlead or a similar warmer with ramp-up enabled

  • Start with 20–50 total sends/day per inbox

  • Aim for a 20–40% reply rate in the first week

  • After one week, increase warm-up volume to 40–50/day

⚠️ Use a completely new domain, not just a subdomain of your main one


Rotate inboxes and swap behavior

To keep your domain healthy long-term:

  • Rotate the inboxes being used in live campaigns

  • Rotate the warmers too, don’t keep the same pattern forever

  • Do a full swap every 2–3 months

✅ Pro tip: forward replies from new inboxes to your main inbox to avoid split conversations


Additional tip: Organize your inbox

Smartlead lets you customize keywords in warm-up emails. You can create filters or folders in Gmail or Outlook to catch these messages and keep them out of your primary inbox view.


What this helps with

  • Maintains high deliverability as you scale

  • Avoids spam traps and IP flags

  • Keeps reply rates strong without manual effort

  • Lets you scale multiple inboxes without splitting your workflow

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