How to warm up a new email domain for cold outreach

A new sending domain has no reputation. If you blast it with cold email on day one, you will end up in spam or get your IP throttled. Warming up is how you build a reputation fast enough to send real volume without getting burned.

Why you need to warm up

Receiving providers (Gmail, Microsoft, Yahoo) track how new senders behave. A brand-new domain that suddenly sends hundreds of cold emails a day looks exactly like a spammer. The result is throttling, spam placement, or a hard block.

Warming up simulates normal, human sending behavior: a small number of emails at first, gradually increasing over weeks. This builds a positive sending reputation so that when you do ramp to real volume, the receivers already trust you.

The basics of a warm-up plan

• Start low: 10 to 30 emails per day on day one.
• Ramp slowly: increase by a small amount each day (often 10 to 20% or a fixed step).
• Keep it consistent: send every day, not in bursts.
• Watch engagement: replies, opens and clicks signal to receivers that your mail is wanted.
• Stop and back off if bounce or spam-complaint rates spike.

How long does a warm-up take?

Most cold email warm-ups run 2 to 4 weeks before you reach full volume. The exact length depends on your target daily volume and how fast you ramp.

For example, to reach 100 emails per day you might start at 10 and add 10 per day, reaching 100 in about 9 days. To reach 500 per day you would need a longer ramp, often 3 to 4 weeks.

The free InboxProof warm-up calculator gives you the exact day-by-day schedule for your target.

What to send during warm-up

During warm-up you want real, engaging email, not junk. Options:

• Warm-up tools: services that exchange emails between their network and yours, building engagement signals.
• Light real outreach: a small number of genuine cold emails each day, well-targeted and personalized.
• Internal or friendly mail: low-risk mail to known recipients to build volume.

The goal is engagement, not just volume. Email that gets opened, clicked and replied to builds a much better reputation than email that is ignored or marked spam.

What to avoid

• Sending to bad lists: high bounce rates during warm-up will tank your reputation fast.
• Ignoring authentication: make sure SPF, DKIM and DMARC are set before you start. See the cold email deliverability guide.
• Ramping too fast: a sudden jump in volume is a red flag to receivers.
• Stopping early: cutting the warm-up short means you hit real volume with a weak reputation.

How to know you are ready

You are ready to send real volume when:

• Your bounce rate is low (under 2 to 3%).
• Your spam-complaint rate is near zero.
• Your open and reply rates are healthy.
• You have completed the full warm-up ramp.

Run a free audit on your sending domain to confirm your authentication and reputation are solid before you ramp.

Want this checked automatically every day? Inboxproof Pro monitors your domain around the clock and alerts you the moment a record breaks or an IP gets listed. See pricing →

Related: Cold email deliverability · Why email lands in spam · SPF vs DKIM vs DMARC · Is my domain blacklisted?