Deliverability
How to warm up an email domain: the 21-day schedule we use
The short answer: Warming up an email domain means sending a small, rising volume of real-looking email from a new inbox for two to three weeks so mailbox providers learn it's legitimate before it carries cold volume. Set up SPF, DKIM and DMARC first, start at 5 to 10 emails a day, add a few each day, keep warmup running at a low level after launch, and never let a new inbox send more than about 30 to 50 cold emails a day. The full schedule is below.
What warmup actually does
Gmail, Outlook and Yahoo score every sending domain and IP on history. A brand-new domain has none, so the first emails it sends are treated with suspicion, and a burst of cold email from it looks exactly like spam. Warmup builds that history on purpose: a small number of emails a day to inboxes that open them, reply to them and pull them out of spam, rising steadily until the domain has a track record.
Warmup can't fix a bad list or a bad email. It buys you a fair hearing.
Before day one
Skip any of these and the warmup is wasted.
- Use a separate domain. Never warm your company's main domain for cold email. Register a variant close to your brand and point it at your website. Our deliverability guide covers why.
- Publish SPF, DKIM and DMARC. Gmail and Yahoo require them for bulk senders, and Outlook.com has rejected unauthenticated bulk mail since May 2025. DMARC at
p=noneis the minimum. - Let DNS settle for 24 to 48 hours. Check records with a lookup tool before sending anything.
- Fill in the profile. A real name, a photo, a signature with a title and the physical address CAN-SPAM requires.
- Age the domain if you can. A domain registered two to four weeks before warmup starts behaves better than one bought yesterday.
The 21-day schedule, per inbox
| Days | Warmup emails a day | Cold emails a day | What to watch |
|---|---|---|---|
| 1 to 3 | 5 to 10 | 0 | Authentication passing on every send |
| 4 to 7 | 10 to 20 | 0 | Spam placement in the warmup network, should be falling |
| 8 to 14 | 20 to 35 | 0 to 10 | Bounces on any test sends, blocklists |
| 15 to 21 | 30 to 40 | 10 to 25 | Reply rate on the first real sends |
| 22 onward | 15 to 25 (keep it on) | 25 to 50 | Daily DNS, blocklist and complaint checks |
Two things people get wrong. First, they switch warmup off at launch. Keep it running at a lower level for as long as the inbox sends cold email. Second, they treat the cold email ceiling as a target. Hunter's 2025 data found inboxes sending 20 to 49 emails a day replied at 5.7%, above average, while exceeding 100 a day damaged deliverability. When you need more reach, add inboxes and domains rather than pushing one harder. Read how many cold emails to send per day for the full math.
Warmup tools
Every major cold email platform includes a warmup network: Saleshandy, Instantly and Smartlead all do. They exchange emails between customer inboxes, open them, reply and rescue them from spam. In our programs Saleshandy's warmup has been the most reliable of the three, which is one reason it's our default for new domains. The tool matters less than the discipline of leaving it on.
What to watch during warmup
- Spam placement in the warmup network. It should fall week over week. If it's still high at day 14, stop and find out why before adding cold volume.
- Google Postmaster Tools. Add every sending domain. Domain reputation should move from "unknown" to "medium" or "high" as history builds.
- Blocklists. Spamhaus, SURBL and URIBL, checked daily. A new domain rarely lands on one unless the content or links trigger it.
- Bounces. Anything above 2% on real sends means the list, not the warmup, is the problem.
How to know a domain is ready
A domain is ready for real volume when all four are true: three weeks of history, spam placement in the warmup network under about 5%, authentication passing on every send, and a small batch of real cold emails that produced replies without bounces or complaints. If any one is missing, give it another week. A week of patience costs less than a burned domain.
Mistakes that undo a warmup
- Sending a big batch on day 22 to "make up for lost time"
- Adding links, images or attachments to the first cold emails
- Sending to an unverified list and bouncing 5% of it
- Running the same copy from ten inboxes on one domain at once
- Turning warmup off to save the tool's monthly fee
At Be Leaded every new inbox follows this schedule before it touches a client campaign, and warmup stays on for the life of the inbox. It's part of why our programs hold a 99% delivery rate.
FAQ
How long does email warmup take?
Two to three weeks before a new inbox sends real cold email, and it keeps running at a lower level afterward. Domains bought a few weeks before warmup starts tend to get through it more smoothly.
How many emails should I send during warmup?
Start at 5 to 10 a day and rise to 30 to 40 by the third week. After launch, keep warmup at 15 to 25 a day alongside cold sends.
Can I warm up my main company domain?
You can, but you shouldn't send cold email from it. If the domain's reputation drops, every invoice, support reply and internal email your company sends suffers. Use separate sending domains.
Should I stop warmup after it's done?
No. Keep it on at a lower level for as long as the inbox sends cold email. Reputation is earned continuously.
Does warmup work for Outlook and Microsoft 365 inboxes?
Yes, and the same schedule applies. Hunter's data shows Google Workspace inboxes replying at 5.9% against 4% or more for Microsoft 365, so many programs run both and let the results decide the mix.
Sources
Keep reading
How many cold emails to send per day, per inbox and per domain
The safe number of cold emails per inbox per day, how many inboxes per domain, and a worked example for reaching 3,000 or 30,000 prospects a month without losing the inbox.
DeliverabilityCold email deliverability in 2026: what Gmail, Yahoo and Outlook require
What Gmail, Yahoo and Outlook require from senders in 2026: SPF, DKIM and DMARC, spam complaint rates, one-click unsubscribe, enforcement dates, and how to set up cold email so it reaches the inbox.
Cold email12 cold email templates that get replies in 2026
Twelve cold email templates we use in client campaigns, with the reasoning behind each one: the trigger email, the question email, the referral ask, the breakup and more. Under 80 words, one ask, no fluff.
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