Email Warmup: How to Warm Up a New Domain or IP, Week by Week

A new email domain or IP address has no reputation. Gmail, Microsoft, and Yahoo have never seen it send, so they have no evidence either way about whether its mail is wanted. Spammers register new domains constantly to escape the reputation of their last ones, which is why providers treat unknown senders with suspicion until proven otherwise.

Warmup is how you provide that proof. You start small, send only to people who will open and click, and increase volume as the positive signals accumulate. Done properly it takes four to eight weeks. Skipped, it produces throttling, spam placement, and blacklist listings that take months to undo.

What happens without warmup

A brand-new domain that sends 50,000 messages on day one looks exactly like someone blasting spam before they get caught. The typical results are:

• Mail is throttled or deferred with temporary errors
• A large share lands in spam
• The IP or domain gets listed on a blacklist
• Google Postmaster Tools shows a "Low" or "Bad" reputation before you have any history to offset it

Recovery from a bad launch takes far longer than the warmup would have.

When you need to warm up

• New domain. Any domain that has never sent email, even one that has hosted a website for years.
• New dedicated IP. The IP has no history, even if your domain does. Moving ESPs usually means new IPs.
• Returning after dormancy. A domain or IP that has been quiet for months has lost most of its reputation. Ramp back up rather than jumping to old volumes.
• New subdomain for email. Subdomains carry some weight from the parent domain but still need their own history.
• Both at once. A new domain on a new IP builds two reputations simultaneously. Be more conservative with every step.

Before you send anything

Authenticate first

Sending unauthenticated mail during warmup kills the process before it starts. Before the first message, confirm:

• SPF includes your sending service. Check your SPF record.
• DKIM is signing and the public key is published. Test your DKIM.
• DMARC is published with at least p=none and an rua address so you receive reports. Check your DMARC record.

Segment your list by engagement

Warmup works by sending to the people most likely to open, click, and reply. Split your list into four tiers before you begin:

1. Most engaged: opened or clicked in the last 30 days
2. Recently engaged: active in the last 90 days
3. Moderately engaged: active in the last six months
4. Unengaged: no activity in six months or more

You will work down this list in order. Tier 4 does not get mailed during warmup at all.

Set up the provider dashboards

Register the domain in Google Postmaster Tools and Microsoft SNDS before the first send. Postmaster Tools shows spam rate and compliance status from the first day Gmail sees enough volume. Without it you are warming up blind.

The week-by-week plan

The targets below suit a list of a few thousand to a few tens of thousands. Scale them with the tables further down if you are much larger.

Week 1: seed contacts (50 to 200 a day)

Gate to pass before week 2: open rate above 30%, zero spam complaints, zero hard bounces.

Week 2: expand cautiously (200 to 500 a day)

Gate: open rate above 25%, complaint rate below 0.05%, hard bounce rate below 0.5%.

Week 3: growth (500 to 2,000 a day)

Gate: open rate above 20%, complaint rate below 0.1%, Postmaster Tools spam rate under 0.1% and no compliance warnings.

Week 4: full ramp (2,000 to 5,000 a day)

Weeks 5 to 8: reach target volume

Increase by 25 to 50% every few days until you reach your intended daily volume. Keep the unengaged tier out until reputation is firmly established, and even then send them a re-engagement campaign rather than your regular content.

Worked example: a 20,000-contact list

Suppose you have moved a 20,000-contact newsletter to a new sending domain. After segmenting, you have 4,000 most engaged, 6,000 recently engaged, 6,000 moderately engaged, and 4,000 unengaged. Your target is a weekly send to the 16,000 engaged contacts, roughly 2,300 a day if you spread it across the week.

Two things make this plan work. First, by the end of week 3 every one of the 16,000 engaged contacts has received at least one message, so the providers have seen a full engagement picture before volume peaks. Second, the 4,000 unengaged contacts never touch the new domain during warmup. Their non-opens and occasional complaints are exactly the signals you cannot afford yet.

If week 2 shows a complaint rate of 0.08%, do not move to week 3. Hold the week 2 volume for three more days, find the source of the complaints (usually a segment that was not as engaged as you thought), and only continue when it is back under 0.05%.

Targets by sender size

Low volume (target 5,000 a week)

Full volume in roughly four weeks.

Medium volume (target 50,000 a week)

Full volume in roughly six weeks.

High volume (target 500,000 a week)

Full volume in eight to ten weeks. At this scale, warm up per provider as well: Gmail, Microsoft, and Yahoo each see their own share of your volume, and one of them can fall behind.

Warmup rules

Send every day

Consistency matters more than volume. Five hundred a day, every day, builds reputation faster than 2,500 once a week. Providers expect regular patterns from legitimate senders, and gaps reset momentum.

Watch the numbers, and stop when they move

Pause immediately if any of these happen:

• Bounce rate above 2%
• Complaint rate above 0.1%
• Delivery rate below 95%
• Postmaster Tools reputation drops to "Low" or "Bad", or the spam rate passes 0.3%
• Your domain or IP appears on a blacklist

Investigate, fix the cause, then resume at the last volume that had clean metrics. Extending warmup by a week costs nothing. Pushing through a warning costs months.

Never mail the unengaged tier during warmup

This is the most common mistake. People who never open your mail generate exactly the signals you are trying to avoid. Save them for after warmup, and send them a re-engagement campaign in small batches, not your regular content.

Send your best content

Warmup mail should be the content people are most likely to open and click. Encourage replies where it makes sense. Every positive interaction is deposited into the reputation you are building.

Add new subscribers gradually, even after warmup

A list import of 10,000 new addresses sent in one go looks like a volume spike. Spread it across days.

Provider-specific notes

Gmail

Gmail learns from engagement and reacts quickly to complaints. Watch the spam rate in Postmaster Tools daily. Since 2024 Gmail requires bulk senders to authenticate, offer one-click unsubscribe, and stay under a 0.3% spam rate, and it applies those rules to new senders from the first day. See Google and Yahoo bulk sender rules.

Microsoft (Outlook.com and Microsoft 365)

Microsoft is cautious with unfamiliar domains and has enforced the same authentication requirements for high-volume senders since May 2025. Register with SNDS for IP-level data. Corporate Microsoft 365 tenants often add their own filtering, so mail to business addresses can take longer to warm than consumer Outlook.com.

Yahoo and AOL

Yahoo tracks complaints from the first message. Enrol in the complaint feedback loop before you start, keep complaints especially low, and expect Yahoo to block more aggressively than Gmail during the first two weeks.

Warmup tools and services

Warmup tools exchange automated messages between accounts they control to generate opens and replies. They can help a cold-outreach domain that has no subscriber list to start with, and they can produce some initial engagement before real sends. They cannot replace real subscribers, providers are increasingly good at recognising the patterns, and artificial engagement does nothing for the domain reputation that Gmail measures from your actual recipients. For any business with an existing list, manual warmup with engaged subscribers is more effective.

When warmup goes wrong

Signs: delivery rate below 90%, bounce rate above 3%, complaint rate above 0.2%, a declining Postmaster reputation, or a new blacklist listing.

Recovery:

1. Pause sending
2. Identify the cause: authentication, list quality, content, or a segment that was less engaged than you assumed
3. Fix it
4. Resume at a lower volume than where you stopped
5. Monitor every send until metrics are stable again

Sometimes it is better to start over on a fresh subdomain. Severe reputation damage, multiple blacklist listings, or a cause you cannot find are all reasons to consider it.

After warmup

Warmup establishes reputation. Keeping it is ongoing:

• Keep monitoring authentication and blacklist status. A DNS change or a rotated DKIM key can undo months of work in a day.
• Remove hard bounces immediately and prune unengaged subscribers regularly.
• Hold complaints under 0.1%. The target does not relax after warmup.
• Ramp any new sending source (a new ESP, a new dedicated IP) the same way.

See email sender reputation for what providers measure once you are at full volume.

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