A new domain has no sending history. Cold outreach from one that hasn’t been warmed is the fastest way to lose it.
Warmup is the four weeks of small, real, engaged sending that gives providers something to judge you on before the volume arrives.
This guide is for cold outreach senders on Google Workspace and Microsoft 365, running a handful of inboxes.
Not for bulk marketing sends through an ESP, which is a different job with different numbers.
Key summary:
- Start at 5 to 10 plain-text emails per inbox per day and ramp over four weeks
- Authenticate first. SPF, DKIM and DMARC must pass before the first send
- Engagement is the signal, not volume. Replies and spam rescues outweigh send count
- Warming a domain and warming each inbox on it are different scopes of the same job
- Running more than one domain? Stagger the domains. The inboxes inside one can start together
Domain Warmup vs Email Account Warmup
Domain warmup builds trust in yourdomain.com. The account kind earns it for a single mailbox sitting on that domain. You do both with the same sending, which is why the two get confused.
Warming an inbox warms the domain it sits on, so these are scopes of one process rather than two.
The distinction matters when several inboxes share a domain, because domain reputation is shared and inbox reputation is not.
| Parameters | Domain warmup | Email account warmup |
|---|---|---|
| What it builds | Reputation for yourdomain.com | Reputation for one mailbox on it |
| Who it protects | Every inbox on the domain | That inbox only |
| When you need it | New domain, or one never used for outbound | New inbox, or one resuming after inactivity |
| If you skip it | Every inbox starts distrusted | That inbox lands in spam while others are fine |
| Typical duration | 3 to 4 weeks | 3 to 4 weeks per inbox |
What Each One Actually Builds
Account warmup builds a behavioural record for one address: this mailbox sends a little, gets replies, isn’t marked as spam.
Domain warmup is that record aggregated. Providers score the domain because it’s the part a sender can’t cheaply discard and replace. That makes it the more durable signal of the two.
So the domain benefits from every inbox on it, and suffers from every inbox on it.
Which One You Need If You Run Multiple Inboxes on One Domain
Both, and you get both from one action: warm every inbox.
You don’t run a separate domain-level process. There is no such setting, in our product or anyone else’s.
What you do control is how many inboxes share the domain, and that turns out to matter more than most guides admit.
That’s observational, not an experiment, and teams running thirteen inboxes on one domain differ from teams running two in more ways than density. It still points one way, consistently. For account-level detail, see our guide to account-level email warmup.
When You Need to Warm Up a Domain (and When You Do Not)
Not every situation needs four weeks. Most cold outreach situations do.
You Must Warm Up If
- The domain is new, especially under 30 days old
- You’re sending cold email from a new inbox, even on an established domain
- You’re switching sending platform, ESP or CRM
- Open rates dropped or bounces rose recently
- The domain has been dormant for months
You Probably Do Not Need To If
- You send under 20 cold emails a day per inbox and placement is stable
- You email existing customers only, from a domain with sending history
Both of those are narrower than they sound. “Placement is stable” means you’ve measured it, not that nobody has complained.
What About an Old Domain That Has Never Sent Email?
Providers judge behaviour, not age.
A ten-year-old domain never used for outbound is effectively new. One with a poor sending history is worse than new, because there’s something to hold against you.
Our own numbers back the first half of that.
Between “under two weeks” and “two to four weeks” there’s about one point of placement, and the curve isn’t even monotonic in between.
Age alone isn’t doing the work people think it is.
Before You Send Anything: Authentication and Domain Checks
Four things, in this order, before the first warmup email leaves.
Set Up SPF, DKIM and DMARC
All three. Not two, and not “we’ll add DMARC later”.
We tested this properly: 20 new accounts across 5 domains, with the authentication stack varied per group.
SPF only, SPF plus DKIM, all three, none, and DKIM plus DMARC with SPF missing.
That lag is why the mistake survives. You check on day three, everything looks healthy, and you conclude the records are optional.
Authentication doesn’t buy you a better week one. It buys you a week three that doesn’t collapse.
Microsoft enforces hardest. Since 5 May 2025, Outlook rejects mail at the SMTP level from domains sending 5,000 or more a day without all three records. Gmail and Yahoo have required the same since February 2024.
Generate the records with our SPF generator, DKIM generator and DMARC generator, then confirm they pass with the header analyzer.
The full walkthrough is in how to set up SPF, DKIM and DMARC.
Then stop touching DNS. Changes mid-warmup restart the clock.
Forward Secondary Domains to Your Primary
A lookalike domain that resolves to nothing is a small negative signal, and removing it takes five minutes.
Point it at your primary site with a 301 redirect.
Anyone who checks — a recipient, a filter, a security team — finds a real company at the other end.
Don’t build a thin copy of your site there. A redirect is the right answer.
Add Profile Pictures and Real Display Names
Use real names on the mailboxes. yash@ and yash.mehta@ are fine. sales2@, info3@ and outreach01@ announce exactly what they are.
Then finish the job. A profile photo, a signature with a job title and a working link, a display name that matches the person. Empty shells look like what they are.
Check the Domain’s Sending History Before You Use It
Do this before you buy, not after. A cheap expired domain can arrive with a blacklist entry attached, and no amount of warmup clears that.
Check it against the major blocklists. Look it up on archive.org to see what it used to be, and search the name.
Five minutes of due diligence beats four weeks of warmup on a domain that was never going to work.
Our blacklist checker guide walks through the lookups.
How Long to Wait Before the First Send
Once DNS has propagated and the records verify, you can start.
That’s usually 24 to 48 hours after you set them, not the two to four weeks some guides recommend.
Waiting longer doesn’t build reputation, because nothing is happening. A domain sitting idle generates no signal at all.
What buying early does buy you is room. Buy domains and mailboxes about a month before you need to send. DNS settling, mailbox setup and four weeks of warmup then fit without anything being rushed.
Verify the records first, then send. Not the other way round.
The Week-by-Week Domain Warmup Schedule
Four weeks from the first warmup email to the first cold one. The numbers below are per inbox per day, not per domain.
| Week | Emails per inbox per day | Send to | Readiness gate before moving up |
|---|---|---|---|
| Week 1 | 5 to 10 | Colleagues, contacts, high-reputation addresses you control | Zero bounces, replies returning, nothing in spam |
| Week 2 | 15 to 25 | Same, plus warm contacts | Bounce under 2%, no spam placement |
| Week 3 | 30 to 50 | Same, widening slightly | Reputation trending up, replies still landing |
| Week 4 | 50 to 60 | Warm contacts only, still no cold sends | Placement stable 5+ days at target volume |
| Week 5+ | Hold warmup at 15 to 20, add cold gradually | Cold outreach begins | Total daily volume doesn’t spike |
The gate column is the instruction and the volume column is the plan. If week two ends with your spam share climbing, you don’t start week three.
Our own cohort data argues against crawling, too. Mailboxes that opened at 8 to 24 a day placed at 88.9% and 90.3% over the following three weeks. The ones that stayed under 8 a day placed at 73.4%.
Read that as association rather than instruction. But “slower is always safer” isn’t what the data says.
What Your Warmup Emails Should Contain
- Plain text only, no links, images, attachments, tracking pixels or UTM tags during warmup
- Never increase more than about 20% in a day, even when engagement looks perfect
- Weekdays only for B2B. Consistency beats coverage
- Spread sends across the working day, roughly 9am to 12pm and 2pm to 5pm
On weekdays-only: Our data puts five-to-six-day sending about 1.5 points of placement below all-seven, which is a fair price for looking like a business.
Missing days at random is a different thing and costs considerably more.
Content should also match what you sell. Warmup that reads like retail promotion, on a domain selling B2B software, teaches providers the wrong thing about the domain.
Warming Multiple Domains and Rotating Inboxes
Past one domain, three questions come up, and two of them have answers most guides get backwards.
How Many Inboxes per Domain
Two or three. Four to six if you need the capacity and accept a small cost.
That’s where our placement data peaks, and the fall past six is steep enough to plan around.
If you need more sending capacity, buy another domain — domains are cheap and placement isn’t.
Staggering Domain Start Dates
The advice you’ll read everywhere is to stagger start dates. It’s worth separating two different things it could mean.
Inboxes on one domain can all start together. That much we’re confident about, from running them at scale. The advice to stagger them has been repeated often enough to sound like a rule, and we’ve not seen it matter.
If you’re bringing several domains live at once and want to be cautious, spacing them out costs nothing but time.
What Inbox Rotation Solves, and What It Does Not
Rotation spreads a day’s cold sending across several inboxes so no single mailbox carries the whole volume. That’s real, and it’s the right answer to a per-inbox sending ceiling.
What it doesn’t do is create reputation. Rotating across ten cold inboxes gives you ten mailboxes with thin histories rather than one with a good one.
It also doesn’t help if all ten sit on one domain, because the domain sees the total either way. Rotation is a volume tool. Warmup is the reputation tool.
Subdomain or Root Domain for Cold Outreach
Never send cold outreach from the domain your invoices go out from. The question is only whether a subdomain is enough isolation.
| Approach | Protects the primary domain | Setup effort | Best for |
|---|---|---|---|
| Root domain | No. Outbound risk lands where your invoices go out from | None | Never, for cold outreach |
| Subdomain | Partially. Providers associate subdomain reputation with the root | Low | Marketing and transactional separation |
| Separate lookalike domain | Yes, fully isolated | Moderate, each needs its own warmup | Cold outreach. The standard |
A separate lookalike domain is the standard for a reason.
Providers do associate a subdomain’s reputation with its root, so a subdomain protects you partially and a separate domain protects you properly.
The cost is that each new domain needs its own four weeks. Plan for that rather than discovering it.
How Long Domain Warmup Takes
Four weeks on a clean new domain. Longer if there’s history to undo, and possibly never if that history is bad enough.
| Starting point | Typical duration | What makes it longer |
|---|---|---|
| New domain, clean history | 4 weeks | Aggressive ramping, sending before authentication resolves |
| Aged domain, never used for outbound | 3 to 4 weeks | Little. No history beats bad history |
| Resuming after long inactivity | 3 to 4 weeks | Resuming at the old volume instead of ramping again |
| Poor sending history | Months, if at all | Blacklist entries, prior complaints |
Providers differ, and by more than people expect. Google Workspace places at 91.5% across our paid traffic against 79.0% for Microsoft 365.
Microsoft also runs more than double the spam rate. If your prospects skew that way, plan for the longer end of every range above.
One thing to expect in week one: the deliverability score you see when you connect a mailbox usually lands between 70% and 90%.
A good day-one number is not a green light. New domains often score high precisely because providers haven’t decided about you yet.
Monitoring, and What to Do When Placement Slips
Check these weekly. If you can’t say what your placement was last week, you aren’t monitoring the domain.
What to Track and Where
| Metric | Healthy during warmup | Where to check | What to do when it slips |
|---|---|---|---|
| Bounce rate | Under 2% | Your sending platform | Above 3%, stop and clean the list |
| Spam complaint rate | Under 0.1% | Postmaster Compliance dashboard, SNDS | Above 0.1%, reduce volume, review targeting |
| Domain reputation | Trending up, no compliance flags | Postmaster Tools (see note), your warmup tool | Flagged 3+ days, hold volume flat, change nothing else |
| Inbox placement | Primary, not Promotions | A placement test | Falling, reduce volume 25 to 30% rather than pausing |
| Reply rate | 25%+ during warmup, 40%+ once outreach starts | Your warmup dashboard | Falling as volume rises means you ramped too fast |
A note on Postmaster Tools. Google retired Postmaster Tools v1 on 30 September 2025, and the domain reputation dashboard went with it. What remains is a Compliance dashboard answering a narrower question.
Microsoft’s SNDS moved portals on 8 June 2026, and its IP data now sits behind an OAuth API.
So guides telling you to watch a green-yellow-red reputation graph are describing something that no longer exists.
Our Postmaster Tools guide covers what replaced it.
The Numbers That Mean Stop
Three thresholds. Cross any of them and stop advancing, immediately:
- Bounce rate above 3%. Stop sending entirely and clean the list before anything else
- Spam complaints above 0.1%. Cut volume and look at who you’re sending to
- Anything in spam during weeks 1 to 2. At 5 to 25 emails a day to contacts you control, nothing should be landing there
None of those means restart. They mean hold.
How to Recover Without Restarting
Reduce volume by 25 to 30%, don’t pause. A pause removes the positive signal along with the negative one, and providers read silence as nothing rather than as an apology.
Then change one thing at a time. Volume first, because it’s the variable most likely to be at fault and the easiest to reverse.
Hold the reduced volume for five to seven days. If placement recovers, resume the ramp from there rather than from where you were. If it doesn’t, the problem isn’t volume and you should be checking authentication and blacklists next.
Domain Warmup Best Practices for Cold Outreach
Authenticate Before You Send
Covered above, and worth repeating because it’s the one people skip. SPF, DKIM and DMARC, verified passing, before email one. Then leave DNS alone.
Avoid Links, Attachments and Salesy Language Early On
Plain text for the whole warmup period. Links and attachments are the two things a filter inspects hardest on an unknown sender.
Salesy language matters less than most guides claim, because reputation outweighs vocabulary. But discount phrasing and heavy formatting steer you into Promotions, which isn’t spam and isn’t the inbox either.
Send Consistently, Not in Bursts
This is the one with the cleanest evidence behind it.
A tenfold bounce gap between gappy sending and daily sending. Some of that runs the other way. A struggling mailbox may send less because its owner gave up. The direction still holds across every band.
Monitor and Adjust Based on Real Signals
Advance on the gate, not the date. Hold when the numbers wobble. Reduce by 25 to 30% when they slip.
The schedule above is a plan. Your account’s numbers are the instruction.
Automate Once You Pass Two or Three Inboxes
Manual warmup works at one or two inboxes if you can sustain it daily for four weeks without missing days. The failure point is consistency rather than effort.
Past three inboxes, generating enough genuine replies by hand stops being realistic. That’s the threshold, and it arrives sooner than people expect.
Best Practices for B2B Domain Warm-Up Specifically
B2B changes four things:
- Weekdays only: Your recipients don’t read business mail on Sunday, and neither should your warmup
- Business providers only: Google Workspace and Microsoft 365 are where your prospects are, so that’s where warmup engagement should come from
- Lower volume, higher engagement: 50 a day with replies beats 100 a day without
- Plan for Microsoft: It filters harder and forgives slower than Google
Checkout Our Email Deliverability Checklist – Get the checklist →
Does Warming a Domain With a Tool Actually Build Reputation?
Yes, and it’s a fair question. The objection behind it is reasonable. If the engagement happens between accounts that agreed to generate it, is a provider really being fooled?
Two honest answers.
The first is that the engagement is real. The mail is genuinely delivered, opened, replied to and rescued from spam by real mailboxes with their own histories. It isn’t a simulation of those events.
The second is that nobody outside Google and Microsoft knows how heavily those signals are weighted, and anyone claiming otherwise is guessing.
What we have is our own testing across 116 million sends, plus what deliverability practitioners compare notes on.
A warmup tool doesn’t trick a filter. It gives an empty sending history something to contain, at a pace a filter can observe.
Where the objection does land is pool quality. A network of accounts created in bulk, on domains with no history, teaches providers that your domain mostly talks to throwaway addresses.
That’s worse than not warming at all. Ask any vendor what its network is made of before you buy.
To compare the options, see our roundup of email warmup tools.
Manual vs Automated Domain Warmup
The honest split is about inbox count and whether you can guarantee daily engagement, not about budget.
| Go manual if you | Go automated if you |
|---|---|
| Are warming one domain with one or two inboxes | Are warming more than one domain, or more than three inboxes |
| Send under 20 cold emails a day per inbox | Are scaling volume or onboarding client domains |
| Have contacts who will genuinely reply, daily, for four weeks | Cannot guarantee daily engagement from real contacts |
| Can check bounce, placement and reputation by hand every day | Need reputation and placement in one dashboard |
| Have time rather than budget | Are recovering a domain or switching platforms |
The middle row is the one that decides it for most people. Four weeks of daily replies from real contacts is a bigger ask than it sounds on day one.
If Your Domain Is Already Burned
Warmup is a reputation builder, not a repair kit. If the domain is listed, warming it changes nothing.
- Check blacklist status first: Warmup will not delist you, and sending while listed makes it worse
- Drop to near zero: Two or three highly engaged contacts, nothing else
- Rebuild far slower than a new domain: Providers watch a flagged domain more closely than an unknown one
- Fix what caused it, or the recovery repeats: A compromised mailbox, an unverified import, a burst that looked automated
- Know when to stop: A repeatedly listed domain is often slower to recover than to replace
That last one is a budget decision, not a technical one. Run the numbers on six weeks of uncertain recovery against a new domain and four clean weeks.
Start with our blacklist checker guide to find out which list, and which sub-list.
Frequently asked questions
1. How long does it take to warm up an email domain?
Four weeks on a clean new domain, from the first warmup email to your first cold send. Three to four weeks for an aged domain that has never sent outbound. A domain with a poor sending history takes months, if it recovers at all. Plan for the longer end if your prospects are mostly on Microsoft 365, which filters harder than Google Workspace.
2. Can I warm up a domain for free?
Manually, yes. You send and reply from every inbox yourself, daily, for four weeks without missing days. It’s genuinely viable at one or two inboxes. Past three, generating enough real replies by hand stops working. Most free plans, ours included, are enough to watch a dashboard rather than to warm a working mailbox.
3. Do I need to warm up an old domain that has never sent email?
Yes. Providers judge sending behaviour, not registration date, so a ten-year-old domain with no outbound history is effectively new to them. The good news is that no history beats bad history. An unused aged domain warms in three to four weeks, the same as a fresh one.
4. How many inboxes should I run per domain?
Two or three, and up to six if you need the capacity. Our placement data peaks at 85.8% with two or three inboxes per domain and falls to 80.0% at seven to twelve. Buy another domain rather than adding a seventh inbox. It’s the cheaper fix by a wide margin.
5. What happens if I skip domain warmup?
Your early cold sends land, because providers let unknown mail through so they can evaluate it. Then placement drops, usually in week two or three, and by then you’ve sent enough bad-looking volume to make recovery slow. Skipping warmup doesn’t delay your results. It costs you the domain, and you start again on a new one having lost more time than warmup would have taken.
6. Can a burned domain be recovered?
Sometimes, and it’s slower than starting over more often than people expect. Delist first, fix the cause, then rebuild at near-zero volume with a handful of engaged contacts. If the domain has been listed more than once, price the recovery against a new domain plus four weeks.
