GuidesWarmup basics

How long does email warmup take?

Every answer quotes a different number of days. This guide shows what Google, Microsoft and Yahoo actually publish, gives a planning figure for each situation, and lists the signs that a mailbox is ready.

Updated 5 October 20269 min read

In short

Plan two to four weeks for a new mailbox on a new domain, and one to two weeks for a new mailbox on a domain that already sends well.
No mailbox provider sets a fixed warmup period. Microsoft's “a couple of weeks or sooner” for a new IP address is the only published duration; Google describes the shape instead: start low, grow slowly, avoid sudden jumps.
A warmup at 10 emails a day gives you a history of 10 emails a day. Real sending has to grow from there in steps.
A mailbox is ready when warmup emails reach the inbox at every provider for a week or more, authentication passes, and no mail is deferred.
Time does not fix missing SPF or DKIM, unwanted content or a poor recipient list.

Plan on two to four weeks for a new mailbox on a new domain, and one to two weeks for a new mailbox on a domain that already sends mail without trouble. These are planning figures, not rules: neither Google nor Yahoo publishes a required warmup period, and the closest thing to an official number is Microsoft’s statement that a new sending IP address “can expect to be fully ramped within a couple of weeks or sooner”. Warmup is over when your mail reaches the inbox at the volume you actually need, not when a calendar says so.

The short answer, by situation

It depends on what already has a history: the domain, the mailbox, or neither.

Your situation	Plan for	Why
New domain, new mailbox	2 to 4 weeks of warmup before the first real campaign	Nothing has a history yet. Google calls consistent volume “particularly important for new domains as they establish their sending reputation”.
New mailbox on a domain that already sends well	1 to 2 weeks	Providers keep reputation per domain, so the mailbox starts with the domain’s standing.
Existing mailbox after more than a month of silence	1 to 2 weeks	The recent history is empty. See warming up again after a break.
Mailbox or domain with recent spam problems	Open-ended: weeks, counted from the day the cause is fixed	Google: “It can take time for improvements in spam rate to reflect positively on spam classification.”
Dedicated IP address at an email service provider	2 to 7 weeks, set by the provider’s plan	Microsoft speaks of “a couple of weeks or sooner”; Amazon SES ramps a new IP over 45 days.

What the mailbox providers actually say

Most answers quote a number of days without saying where it comes from. Here is what the companies that run the inboxes have published, as of October 2026.

Google

Google’s Email sender guidelines have a section titled “Increase sending volume slowly”. It gives no number of days. It describes a shape:

Start with a low sending volume to engaged users, and slowly increase the volume over time.

Avoid introducing sudden volume spikes if you do not have a history of sending large volumes. For example, immediately doubling previously sent volumes suddenly could result in rate limiting or reputation drops.

The only growth rate Google names is in its Top 10 Gmail sender issues, in the advice for senders whose mail was temporarily refused: pause, send below the level that caused the problem for 24 hours, then “slowly increase your sending volume, with a common daily increase of 25% to 100% depending on various factors”. All of this is written for mail to personal Gmail accounts; Google’s FAQ says the guidelines do not apply to mail sent to Google Workspace inboxes.

Microsoft

Microsoft’s Outlook.com Postmaster troubleshooting page is the one place where a provider puts a duration in writing. It explains that IP addresses that have not sent mail before typically have no reputation yet and are more likely to run into delivery problems, and then:

A new IP can expect to be fully ramped within a couple of weeks or sooner depending on volume, list accuracy and as long as their junk email complaint rates are kept at a minimum.

The same page says a good domain shortens the wait. New IPs added under a domain’s existing SPF record (the DNS entry that lists who may send for the domain) “typically experience the added benefit of inheriting some of the domain’s sending reputation”. That is the documented basis for giving a new mailbox on an established domain less time.

Yahoo

Yahoo’s Sender Hub names no duration either. Its FAQ states the risk that a warmup is meant to avoid: “If you send emails at a certain rate and suddenly have a spike of activity, you could get flagged as a compromised sender and marked as spam.”

Email service providers, for their own IP addresses

Companies that send mail for others publish firmer schedules. Amazon SES warms a new dedicated IP automatically “over 45 days”. Twilio SendGrid adds a caution: “A gradual warmup doesn’t guarantee a perfect sending reputation.”

The documents agree on the shape: start low, grow in steady steps, avoid jumps, slow down when mail is refused. They leave the length to you. “Two to four weeks” is a convention that fits this shape at the volumes a single mailbox sends.

What happens during those weeks

If your mailbox is at Google Workspace or with a hosting company, you send from their IP addresses, which you share with other customers. You are not warming an IP. You are building a history for your domain. Google says Gmail “tracks volume, feedback, and limits per domain and IP address”. Yahoo says “each IP and DKIM domain has a reputation”; DKIM is the signature that ties a message to your domain. Without SPF and DKIM for your own domain, that history has nothing of yours to attach to.

A warmup tool connects to your mailbox and makes it exchange short emails with other mailboxes in a shared pool. Some of them get a reply. When one lands in a spam folder, the receiving mailbox moves it back out. Gmail’s help describes what that does for the person who does it: “After you remove the email, future emails from that sender won’t go to Spam.”

After a few weeks, the domain has a record of authenticated mail at a steady, slowly growing volume that nobody reported as spam.

Two things are not documented. No provider says how much weight it gives to mail exchanged in a pool compared with mail between people who know each other. And one common claim runs against Google’s own text: descriptions of warmup often list opened emails among the signals that build reputation, while the sender guidelines state that “Google doesn’t track open rates”.

A warmup, day by day

Here is a real ramp, the one WarmupBay uses: 3 emails on the first day, one more each day, up to the daily target. The free target is 10 emails a day. With a badge on your website it is up to 30.

Day	Emails that day (target 10)	Sent so far	Emails that day (target 30)	Sent so far
1	3	3	3	3
5	7	25	7	25
8	10	52	10	52
14	10	112	16	133
21	10	182	23	273
28	10	252	30	462

The free target is reached on day 8, the higher one on day 28. The largest step is the first, from 3 to 4, a third more. From the second week on, each day adds a tenth or less. That starts near the low end of the daily increase Google mentions and soon falls below it.

Reaching the target is not the end of the warmup. From there the volume stops growing and starts being consistent, and consistency is the part that takes weeks.

Is two weeks enough?

Sometimes. For a new mailbox on a domain with a clean history, two weeks of steady warmup is a reasonable plan. For a brand-new domain it is the short end: Microsoft’s “couple of weeks or sooner” assumes that volume, list accuracy and complaint rates go well.

What two weeks never buy is a jump. Whatever level the warmup reached, your real sending has to continue from about there. A mailbox that exchanged 10 emails a day has a history of 10 emails a day. It does not have a history of 200. Google’s example of what to avoid, “immediately doubling previously sent volumes”, applies on the day after the warmup just as it did on the first day.

How do you know the mailbox is ready?

No provider sends a notice. Look for these signs together.

Warmup emails arrive in the inbox, at every provider, for a week or more. WarmupBay’s dashboard shows where each day’s emails landed (inbox, a Gmail tab, or spam) separately for Google and for other providers. It shows an inbox rate only once it has 20 deliveries to count, which at the starting pace is day five at the earliest.
Authentication passes on every message. SPF, DKIM and DMARC, the three DNS-based checks that show a message really comes from your domain, should all read “pass” in the headers of a message you send to yourself.
No temporary refusals. When a provider thinks you are going too fast, it defers your mail with a code that starts with 4. You see it as a “delivery delayed” notice or in your sending tool’s log.
Your ordinary mail still arrives. If customers start finding your replies in spam, stop increasing and find out why.

These are the deferrals to recognise, as listed in Google’s SMTP error reference and on Microsoft’s troubleshooting page:

421 4.7.28 Gmail has detected an unusual rate of email. To protect our
users from spam, email has been temporarily rate limited.

421 RP-001 The mail server IP connecting to Outlook.com server has
exceeded the rate limit allowed. Reason for rate limitation is related
to IP/domain reputation.

A code in the 400 range is temporary: the mail standard, RFC 5321, says “the error condition is temporary, and the action may be requested again”. Google’s instruction for this case is to “reduce the sending volume until the SMTP error rate decreases. Then, increase slowly again.”

What makes it take longer

Missing authentication. Google requires SPF or DKIM from everyone who sends to Gmail. A warmup without them builds nothing. WarmupBay checks SPF, DKIM and DMARC when you connect a mailbox and shows a ready-made DMARC record. If the records are still missing after 72 hours, it stops the warmup.
A history of complaints. Google asks senders to keep the spam rate “below 0.10%” and to “avoid ever reaching a spam rate of 0.30% or higher”. A domain above that line has to repair its record before a warmup can add to it.
Real campaigns added too early or too fast. Fifty cold emails on day six are a spike, whatever the warmup tool does next to them.
Stop-and-go sending. The M3AAWG Sender Best Common Practices, guidance from an industry anti-abuse working group (version 3.0, 2015), put it this way: “Consistency of volume, whether high or low, plays an integral part in the determination of IP reputation and deliverability outcomes.”

When the warmup is done, do you switch it off?

A warmup has no finish line. It is the first stretch of a sending history, and the history goes on with whatever you send next.

The useful question is whether your own mail now provides what the warmup provided: steady volume to people who want it. If you send every working day and people answer, the pool adds little. If your sending comes in bursts, a small constant flow evens it out. Tool vendors generally recommend keeping warmup on. No mailbox provider documents an answer either way.

If everything stops for a while, you will not need the full warmup again in most cases. Warming up again after a break covers how long a pause is harmless and how to come back.

Where WarmupBay fits, and where it does not

WarmupBay is a free warmup pool that runs the ramp shown above. Warmup emails that land in spam are taken out again, and everything is filed in a folder called “WarmupBay”, away from your own mail. The higher limit of 30 a day holds for as long as the badge stays visible in your website’s footer. There is no paid plan and no credit card; the details are under Free, forever.

For the timeline in this guide, that means a new mailbox gets its first weeks of steady, authenticated mail without you sending anything by hand. You can connect a mailbox and follow where that mail lands in the dashboard.

What it does not do:

It does not guarantee the inbox. Nothing does. What you write and who you write to still matter.
Ten or thirty emails a day give a mailbox a steady start. They are not a history for sending hundreds a day.
It connects Gmail and Google Workspace with an app password, and other providers over IMAP and SMTP. Microsoft 365 and Outlook.com mailboxes cannot be connected yet.
One mailbox per account.
It is new. It launched in October 2026.

Questions people ask

Can I send real emails while the warmup is running?

Yes. The mailbox stays yours, and ordinary correspondence with people who answer you only adds to its history. Hold back campaigns to people who do not know you until the warmup has run for a couple of weeks, then add them in small numbers and grow from there.

Are 10 warmup emails a day enough?

No provider publishes a minimum. What the documentation stresses is consistency: the M3AAWG sender practices say consistency of volume matters “whether high or low”. Ten a day gives a new or resting mailbox steady activity. It does not prepare a mailbox for hundreds of emails a day; that volume has to be built up with real mail.

Does warmup go faster if I send more warmup emails a day?

No. The wait is about a steady record over time, not about a total number of emails. Google's guidelines say that the more email you send, the more slowly you should increase the volume. A higher daily target makes the ramp longer, not the warmup shorter.

Does every new mailbox on my domain need its own warmup?

A short one, yes. The domain's standing carries over, which is why one to two weeks is a sensible plan instead of four. But a mailbox that goes from no mail to full volume overnight is still a sudden rise in what your domain sends, and that is what the providers warn against.

Does email warmup still work in 2026?

The part the providers describe themselves still holds: Google tells senders to start low and increase slowly, Microsoft says a new IP address has no reputation until it has built one, and Gmail's help says mail from a sender you took out of spam will not go to spam for you again. What a pool cannot do is make unwanted mail welcome. Gmail's program policies say that when users mark emails as spam, future messages from that sender are more likely to be classified as spam. A warmup cannot be expected to cancel that out.

I warmed up for a month and my emails still go to spam. What went wrong?

Then time was not the missing piece. Check that SPF, DKIM and DMARC pass on the messages that go to spam, and look at what those messages say and who receives them. If your warmup emails reach the inbox and your campaign does not, the campaign is the cause. Google also notes that after spam rates improve, it can take time for its classification to follow.