How long does it take to warm up a domain?
Vendors' answers run from 1 to 2 weeks up to 8 to 15 weeks, and the mailbox providers that decide where your mail lands give no warm-up period for a new domain. As of 20 October 2026, Google's sender guidelines describe how to raise volume but not over how long, and the Microsoft pages we checked set lower limits for new accounts and tenants without giving a warm-up schedule.
Smartlead, which sells cold email software, sums up the spread on its warm-up benchmark page: "Published guides advise anywhere from 2 weeks to 3 months for a new domain." The same page reports what senders actually do on its platform: the average new mailbox warms up for 8 days before its first campaign, down from 9.4 days a year earlier.
We found no independent study that compares warm-up length with inbox placement or replies. Smartlead says its own data can't tell you whether 8 days is enough, because it doesn't compare reply rates by warm-up length and doesn't separate brand-new domains from aged ones. So the useful answer has three parts: what the vendors claim, what the providers publish, and a schedule you choose with both in view.
What do warm-up vendors say?
Each vendor below gives a different number on its own page. All of them sell warm-up or cold email sending tools.
| Vendor and page | Recommended warm-up | What the number covers | Page date |
|---|---|---|---|
| Mailshake help article | At least 1 to 2 weeks before outreach | For a brand-new domain, it also suggests waiting 7 or more days after creating it before warm-up starts | Updated 2 Jul 2025 |
| Instantly blog | Minimum 2 weeks, typically 3 to 4 weeks before cold outreach | Full sending volume at 4 to 6 weeks; the 2026 benchmark report it cites gives this as advice (start at 5 to 10 a day, increase over 4 to 6 weeks) without data on timing | Published 3 Dec 2024, updated 16 Oct 2026 |
| Smartlead warm-up guide | Minimum 30 days for a new domain; its FAQ says 3 to 4 weeks | Warm-up before campaign sends | Published 6 Oct 2026 |
| Warmy blog | Gains typically show in 3 to 5 weeks; warmed by around day 45 | Its own day-by-day manual schedule | Dated 16 Sep 2026 |
| lemlist help centre | About 40 days of warm-up ramp, then 14 days at target: about 54 days | Before a new mailbox sends any cold email | Checked 20 Oct 2026 |
| Mailivery help article | 8 to 15 weeks | Only if you don't plan to keep warming afterwards | Shown as updated a year ago |
| Smartlead benchmark | No recommendation: the average sender waits 8 days | What senders on its platform did, from more than 850 million emails | Undated; checked 20 Oct 2026 |
Two rows deserve a second look. Smartlead's guide asks for at least 30 days while its benchmark shows the average sender waits 8, and Smartlead itself says the 8 days is what senders do, not a proven minimum. And the longest figure, Mailivery's 8 to 15 weeks, is for people who plan to stop warming afterwards; Mailivery's own recommendation is to keep the mailbox connected to its service.
Why do the vendors' numbers differ so much?
They measure different finish lines and different starting lines, and none of them publishes a test of one length against another.
- Different finish lines. Instantly separates ready for cold outreach (3 to 4 weeks) from full sending volume (4 to 6 weeks). lemlist counts until a mailbox may send its first cold email. Mailshake counts until outreach starts.
- Different starting lines. Mailshake suggests waiting 7 or more days after registering a brand-new domain, then connecting one address and waiting a month before connecting the rest. lemlist treats a domain under a month old as a special case and keeps the whole domain under 100 emails a day.
- Gates that aren't measured in days. Instantly requires a warm-up health score above 90% before an account is campaign-eligible. lemlist requires a Warmup Score of 90 and 14 days of stabilisation with an inbox rate above 90%.
- Commercial interest. Every vendor here earns money from warm-up or sending, and none of these pages cites outside research for its number.
The practical reading is to compare like with like. Some figures mark the earliest first campaign, some mark full volume, and Mailivery's covers a mailbox that stops warming afterwards. Pick the finish line you care about before you compare numbers.
What does Google say about new domains and ramping volume?
Google describes how to ramp up and gives no timetable. Its email sender guidelines, written for mail sent to personal Gmail accounts, have a section on increasing sending volume slowly. It names three factors that set how fast you can increase: how much you send (the more email, the more slowly you should increase), how often you send (you can increase faster when you send daily instead of weekly), and recipient feedback.
For senders of large amounts of email, the guidelines recommend:
- Send at a consistent rate and avoid bursts.
- Start with a low volume to engaged users and increase slowly over time.
- As volume rises, monitor server responses, spam rate and the sending domain's reputation.
- Avoid sudden spikes if you have no history of large volumes. Google's example: "immediately doubling previously sent volumes suddenly could result in rate limiting or reputation drops."
- If messages start bouncing or being deferred, reduce volume until the SMTP error rate falls, then increase slowly again.
Two more Google rules affect new senders. The sender guidelines FAQ defines a new domain as one that hasn't sent more than 5,000 emails a day to personal Gmail accounts since 1 January 2024, and says enforcement of the bulk-sender rules will move on an accelerated timetable for new domains. And on Google Workspace, a trial account can send 500 messages a day, and limits aren't raised during the trial. After you convert to a paid plan, limits rise automatically once your domain has paid at least $100 in total (the domain's cost plus $100 if you bought it from Google), and Google says that can take up to 75 days after you reach the threshold.
What does Microsoft say about new tenants and accounts?
Microsoft sets lower limits for new tenants and new accounts and gives a rough ramp time for new sending IPs, though none of the Microsoft pages we checked gives a warm-up schedule for a domain.
- New Microsoft 365 tenants. Microsoft's tenant outbound limits post, updated 13 August 2026, says changes to how the external recipient quota is calculated for certain tenants would begin rolling out from 14 September 2026. It lists reduced quotas for newly created tenants: 10% of the standard quota for a tenant less than 31 days old, 25% at 31 to 60 days, and the full quota after 60 days. For a one-licence tenant, whose standard quota is 10,000 external recipients a day, that works out at 1,000 a day in the first month and 2,500 in the second.
- New Outlook.com accounts. Microsoft Support's Outlook.com sending limits page says a newly created account gets a low sending quota as a temporary restriction, raised to the maximum once the account establishes credibility. Its tips for raising limits include completing your profile, adding the people you email to your contacts and emailing them often.
- New sending IPs. The Outlook.com Postmaster troubleshooting page says a new IP can expect to be fully ramped within a couple of weeks or sooner, depending on volume, list accuracy and low junk complaint rates. New IPs added for a domain already covered by its SPF record typically inherit some of that domain's reputation.
Yahoo's sender pages give no ramp schedule either. Its sender FAQ says a new sender, or one with a new IP, who has trouble delivering to Yahoo can file a Sender Support Request, and that Yahoo has no whitelisting programme. Its SMTP error codes page lists a recently set-up sending IP whose traffic was not increased slowly as one possible cause of errors for excessive unsolicited mail.
A conservative eight-week warm-up schedule
Plan on eight weeks of ramp from a new domain before a mailbox reaches full cold volume. That is longer than Instantly's 4 to 6 weeks to full volume, shorter than lemlist's path (about 54 days to the first cold email, then about three weeks of weekly steps to its cap) and at the low end of Mailivery's 8 to 15 weeks. This schedule is our advice; it is neither a provider rule nor a tested result. Its first cold emails, in week 3, come at Instantly's 2-week minimum and before Smartlead's 30 days, so keep them few.
| When | Cold emails per mailbox per day | What to do |
|---|---|---|
| Before week 1 | 0 | Register the domain. Set up SPF, DKIM and DMARC (p=none to start), create the mailbox, and add the domain to Google Postmaster Tools. |
| Weeks 1 and 2 | 0 | Warm-up only. Send some real one-to-one email to people who know you and will reply. |
| Weeks 3 and 4 | 5, then 8 | First cold emails, to your best-fit contacts with verified addresses. Keep warm-up running. |
| Weeks 5 and 6 | 10, then 14 | Raise only if bounces and deferrals stayed flat the week before. |
| Weeks 7 and 8 | 18, then 24 | Same check each week. Send every weekday rather than in weekly batches. |
| Week 9 onwards | Up to about 30, then hold | For more volume, add mailboxes instead of pushing this one. Keep some warm-up running. |
Three rules sit on top of the table, all based on Google's guidelines. Never jump to double the previous volume; each step above adds no more than about 60%. If bounces or deferrals rise, drop back a step until the errors fall, then climb again more slowly. And send daily: Google says daily senders can increase volume faster than weekly ones.
If you send through Siela's AI SDR, set the daily email goal to match the week you're in. The goal is a target, not a quota, and the most a Gmail mailbox will send is 150 a day; the ramp is up to you.
What to do this week
Start the clock now, because the warm-up period is time you can't buy back later. Each step below takes under an hour.
Check how new your domain is
If the sending domain was registered this month, treat it as brand new: lemlist's help centre keeps a domain under a month old below 100 emails a day across all its mailboxes.
Authenticate before you warm up
Set up SPF, DKIM and DMARC first. Google requires SPF or DKIM from every sender to personal Gmail accounts, and Instantly's guide says to authenticate the domain before any warm-up.
Check your account limits
If your Google Workspace account is still a trial, it is capped at 500 messages a day. If your Microsoft 365 tenant is under 61 days old, its external recipient quota may be cut to 10% or 25% of the standard figure.
Set up monitoring
Add the domain to Google Postmaster Tools so you can see spam rate and reputation as volume rises.
Put the ramp in your calendar
Write the weekly targets from the schedule above into your calendar with a review every Friday. Meanwhile, draft the sequence you'll send in week 3; our cold email sequence guide and cold email templates are a place to start.
Frequently asked questions
Can I send cold email from a brand-new domain right away?
Google's and Microsoft's pages set no waiting period, but both make a fast start harder. Google's guidelines tell large senders to start with low volume to engaged recipients and increase slowly, and Microsoft gives tenants less than 31 days old 10% of their standard external recipient quota. Every warm-up vendor we checked advises at least one to two weeks of warm-up first.
How long should I wait after registering a domain before warming it up?
Vendors disagree. Mailshake suggests waiting 7 or more days after creating a brand-new domain, then connecting one address and waiting a month before adding the rest. Smartlead's guide, for teams running many domains, says to start warm-up as soon as the domain is registered. lemlist keeps a domain under a month old below 100 emails a day in total.
Does Google publish a warm-up schedule for new domains?
No. Google's email sender guidelines give no number of days or weeks. They say to start with a low volume to engaged users, increase slowly, send at a consistent rate, avoid sudden spikes and watch spam rate and reputation. They add that daily senders can increase volume faster than senders who mail weekly.
When do Google Workspace sending limits increase for a new account?
Trial accounts are limited to 500 messages a day, and Google says limits aren't increased during the trial. After you convert to a paid plan, limits rise automatically once your domain has paid at least $100 in total, or the domain's cost plus $100 if you bought it from Google. Google says this can take up to 75 days.
Should I keep warming up after campaigns start?
The vendors say yes, and all of them sell warm-up. Instantly suggests keeping 20 to 30 percent of daily volume on warm-up. lemlist says to keep one reputation signal running: inbox placement tests once or twice a month, or warm-up at 10 a day. Smartlead's guide says to run warm-up alongside campaigns indefinitely.
Sources
- Gmail Help: Email sender guidelines (checked 20 Oct 2026)
- Gmail Help: Email sender guidelines FAQ (checked 20 Oct 2026)
- Google Workspace Help: Gmail sending limits in Google Workspace (updated 13 Oct 2026)
- Exchange Team Blog: Introducing Exchange Online Tenant Outbound Email Limits (published 24 Feb 2025, updated 13 Aug 2026)
- Microsoft Support: Sending limits in Outlook.com (checked 20 Oct 2026)
- Yahoo Sender Hub: FAQs (checked 20 Oct 2026)
- Mailshake Help: How does Email Warmup work? (updated 2 Jul 2025)
- Instantly: How to Warm Up a New Email Domain For Cold Email Outreach (published 3 Dec 2024, updated 16 Oct 2026)
- Smartlead: Email Warm-Up Guide (published 6 Oct 2026)
- Smartlead Benchmarks: How long should you warm up an email domain before a campaign? (checked 20 Oct 2026)
- Warmy: How Long to Warm Up a New Email Domain? (16 Sep 2026)
- lemlist Help Center: Understand sending limits in lemlist (checked 20 Oct 2026)
- Mailivery Help Center: For how long should I warm a mailbox? (shown as updated a year ago; checked 20 Oct 2026)
- Siela: AI SDR (checked 20 Oct 2026)
- Instantly: Cold Email Benchmark Report 2026 (updated 12 Jan 2026)
- Outlook.com Postmaster: Troubleshooting (checked 20 Oct 2026)
- Yahoo Sender Hub: SMTP Error Codes (checked 20 Oct 2026)