How to warm up an email domain for cold email

You want to send cold email to buyers who do not know you yet, and you have heard that almost all of it lands in spam now. This guide shows you how to warm up an email domain for cold email: new domains, the right settings, and a slow start that gets you to 100 new people a day from week 3, with every follow-up running by week 6. If you skip the warm-up and send 100 emails on day one from a new domain, most of them go to spam, and you cannot tell whether anyone would have replied.

Do these three things

About 3 hours today, then 30 minutes a day. Cold email reaches full volume in week 6. Judge it after 2,800 first emails.

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1. 1Today: buy 5 new domains for cold email, make 3 mailboxes on each, turn on SPF, DKIM and DMARC, and start warm-up on all 15 mailboxes.
2. 2Every day: for the first 2 weeks, send only warm emails from the new mailboxes, and send the rest of your 100 messages on LinkedIn and by phone. From week 3, raise each mailbox from 10 cold emails a day to 30 by week 6.
3. 3Every Sunday: check each mailbox's bounces, replies and health score. Rest any mailbox that fails, and keep one spare domain warming so a failed one never stops your 100.

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1. Buy 5 separate domains for cold email, never your main one

Buy new domains for cold email and never send it from the domain your clients and team use. If strangers mark your cold email as spam, the damage stays on the new domain, and your normal email keeps working.

Why 5. Your target is 100 personal emails to new people a day, and each person gets up to 3 follow-ups. Once the follow-ups are running, that is up to about 400 emails a day, fewer as people reply. One mailbox should send no more than 30 a day (step 4), so you need about 14 mailboxes. Put 3 on each domain: 5 domains give you 15 mailboxes and room for 450 a day. More domains also mean one bad week on one domain stops only a fifth of your email.

How.

1. Pick 5 names close to your main one, so a buyer can tell it is you: get[yourname].com, [yourname]hq.com, try[yourname].com, [yourname]team.com, use[yourname].com. Use .com where you can.
2. Buy them at Cloudflare Registrar. It sells .com domains at cost, about $10.44 a year each, and the price does not jump when you renew. Its DNS settings, where you add the records in step 2, are free.
3. In Cloudflare, add a redirect rule on each new domain that sends visitors to your main website. Buyers who get your email often type the domain to check you. They should land on your real site, so your website has to say what you do and who it is for, and give them a way to get in touch.

Decide your budget now. The full setup costs about $52 a year for the domains, $126 a month for 15 mailboxes (step 2) and $97 a month for the sending tool once cold email starts (step 3). That is about $225 a month. If that is too much today, buy 2 domains and make 6 mailboxes. Six mailboxes carry about 45 new people a day with their follow-ups. Send the other 55 of your 100 messages as LinkedIn messages and calls, and add 3 mailboxes for every $25 a month you can add. Do not lower the 100. Spread it. If you are working out where the money comes from, set a marketing budget first.

• Tool: Cloudflare Registrar, about $10.44 a year per .com domain.
• Time: 30 minutes.
• You will have: 5 new domains, each sending visitors to your main website.
• It worked if: you type each of the 5 domains into a browser and land on your main site.
• Common mistake: sending cold email from your main domain "just to test". One bad week can push your client emails and invoices into spam too. The other mistake is a typo version of your name, such as [yourname]-mail.net. It looks like a fake, and buyers delete it.

If you run an agency: never warm up or send cold email from a client's main domain. Buy separate domains in the client's name and write it into the scope of work when you onboard the client. To find your own first clients, use your own 5 domains and a cold email written for agencies.

If you run a D2C store: use these mailboxes only for businesses: shops that could stock you, distributors and creators who list a business email. Never cold email shoppers. In the UK, you need a person's consent before you email them marketing, and that includes sole traders.

2. Create 3 mailboxes on each domain and set up SPF, DKIM and DMARC

Create 3 real mailboxes on each new domain, and turn on SPF, DKIM and DMARC before any of them sends a single email. These three settings prove to Gmail, Outlook and Yahoo that your emails really come from you.

Why now. Gmail asks every sender to set up SPF or DKIM and to keep spam reports below 0.3%, and it suggests staying under 0.1%. Since November 2025, Gmail has been rejecting more mail that breaks these rules, and new domains get less time to get it right. Yahoo has the same rules. Outlook.com has required SPF, DKIM and DMARC from bulk senders since 5 May 2025. The strict bulk rules start at 5,000 emails a day, far above you, but set up all three anyway: they protect your email deliverability, and they take an hour.

How.

1. Create the mailboxes. Sign up for Google Workspace Business Starter with your first new domain. Add the other 4 as secondary domains (no extra cost). Add 3 users on each domain, each with a real name: your first name, your first name and initial, and "hello.[firstname]". That is 15 paid seats at $8.40 a month each on the flexible plan, or $7 a month on a 1-year plan. Workspace's free trial stops at 10 users, so adding the 11th starts billing. That is expected.
2. SPF. In Cloudflare's DNS for each domain, add one TXT record on the domain itself: v=spf1 include:_spf.google.com ~all. Each domain gets exactly one SPF record.
3. DKIM. In the Google Admin console, go to Menu, then Apps, then Google Workspace, then Gmail, then Authenticate email. Pick the domain, click Generate new record, choose 2048, and add the TXT record it shows in Cloudflare. Back in the Admin console, click Start authentication. It can take up to 48 hours to work. Do it for all 5 domains.
4. DMARC. Add one TXT record named _dmarc on each domain: v=DMARC1; p=none; rua=mailto:[a mailbox you read]. Start with p=none, which only reports. Move to p=quarantine once a month of reports shows only your own mail.
5. Make each mailbox look like a person. Add a real photo, the same one as on your LinkedIn profile, and a plain signature: your name, your company, your main website and your postal address. In the US, the CAN-SPAM Act has no exception for business email: every commercial email needs your postal address and a clear way to say no, and you must honour a "no" within 10 business days. Put the "no" line in the email itself.
6. Check. Send one email from each mailbox to your own personal Gmail. Open it, click More (the three dots next to Reply), then Show original. SPF, DKIM and DMARC should each say PASS.

• Tool: Google Workspace Business Starter, $8.40 per mailbox a month. Cloudflare DNS, free.
• Time: 1 hour 30 minutes for all 15, plus up to 48 hours for DKIM to start.
• You will have: 15 mailboxes on 5 domains, each with a photo, a signature and all three records.
• It worked if: Show original says PASS three times for every one of the 15 mailboxes.
• Common mistake: two SPF records on one domain, for example one from Google and one from an old website host. Inboxes then treat SPF as broken. Merge them into one line.

[First name] [Last name]
[Company] · [main website, as plain text]
[Street address, city, postcode, country]If this isn't useful, reply "no" and I won't email you again.

3. Turn on warm-up and send only warm emails for the first 2 weeks

For the first 14 days, send no cold email at all. Let a warm-up tool send and answer a few emails from each mailbox, and send your own real emails to people who already know you.

Why 2 weeks. A new domain has no history. Gmail's own advice is to start with a low volume to people who want your email, and raise it slowly. Instantly, the tool below, says a mailbox is ready for cold email after at least 2 weeks of warm-up and a health score above 90%. Real replies from people who know you show inboxes the strongest sign that your email is wanted, so do both.

How.

1. Turn on the warm-up tool. Sign up for Instantly's Growth plan, $47 a month. It allows unlimited mailboxes and unlimited warm-up, and its free trial allows only 2 mailboxes. In Instantly, go to Email Accounts, click Add New, choose Google, then Option 1: oAuth. Follow its steps to allow Instantly in your Google Admin console, then connect all 15 mailboxes. Turn warm-up on for each and keep the default settings: Increase per day 1, Daily warmup limit 10, Reply rate 30%.
2. Send 2 warm emails a day from each mailbox. That is 30 a day across all 15. Send them to people who already know you: past colleagues, old clients, suppliers and friends in your buyers' industry. Ask each one for one introduction, as in the first-clients routine. People who know you reply, and every reply helps the new mailbox. ChatGPT or Claude drafts each one from a line you give it about the person; you read it and send it. That is about a minute an email. If you run out of people you know, let the warm-up tool carry the rest. Do not fill the gap with strangers.
3. Keep your 100 a day going. The 30 warm emails count toward the 100 messages a day in your B2B marketing routine. Send the other 70 as LinkedIn messages to people who fit, and as calls to the smallest companies on your list. Use these 2 weeks to build your lead list to at least 1,400 named buyers, with a checked email address for each, ready for week 3.

• Tool: Instantly Growth plan, $47 a month. ChatGPT or Claude to draft the warm emails.
• Time: 1 hour today to connect the mailboxes. Then about 30 minutes a day for the 30 warm emails.
• You will have: 15 mailboxes warming every day, and 420 warm emails sent by day 14.
• It worked if: on day 14, every mailbox shows a Health Score above 90% in Instantly's Email Accounts page, and at least some of your warm emails got real replies.
• Common mistake: "just a few" cold emails in week 1. It is exactly what Gmail sees as a new spammer. The other mistake is turning warm-up off once cold email starts. Keep it on for as long as the mailbox sends.

If you run a SaaS: your warm emails can go to your current signups and beta users, asking what made them try it. They reply, and you learn your buyers' words for the cold email, the same way customer interviews do. It also feeds your first 100 users.

4. Start cold email at 10 a day per mailbox and reach 30 a day by week 6

On day 15, start cold email at 10 a day from each mailbox, and raise it every week until each one sends 30 a day in week 6. With 15 mailboxes, you can send 100 first emails a day from week 3.

The ramp. Instantly recommends 30 campaign emails per mailbox a day, with warm-up on top. Hunter's 2026 report on 31 million emails found the best reply rate, 5.7%, from mailboxes that sent 20 to 49 a day. Thirty sits inside that range and leaves room for a mailbox that has a bad day. The 30 counts first emails and follow-ups together. Warm-up emails do not count.

In weeks 3 to 5, some follow-ups will not fit. The tool sends them a day later. That is fine. Keep the 100 first emails.

How.

1. In Instantly, go to Email Accounts, click each mailbox, open Settings and set Daily Campaign limit to 10. Raise it every 7 days: to 15 for week 4, 20 for week 5 and 30 from week 6.
2. Move to Instantly's Hypergrowth plan, $97 a month, before day 15. Growth stops at 5,000 emails a month, and you will send about 12,000 once follow-ups run.
3. In each campaign's Options, turn off Open tracking and Link tracking, and turn on "Send emails as text-only (no HTML)" and "Stop sending emails on reply". Tracking adds hidden images and changed links that spam filters look for. Lemlist, another cold email tool, now tells its users to turn both off.
4. Load only addresses you have checked. A bounce is an email to an address that does not exist, and too many tell inboxes your list is bought. Keep bounces under 2%.
5. Every email is still written for one person. AI drafts each one from a row in your sheet, and you add one true line about the person (how to write it). The tool only spreads the emails across your mailboxes and keeps each one under its limit. Sending the same text to everyone is spam, whatever the setup.

• Tool: Instantly Hypergrowth, $97 a month. Your lead list in a Google Sheet.
• Time: 15 minutes a week to change the limits. Writing the 100 daily emails is its own job: about 2 hours a day with AI drafting, so plan it into your week.
• You will have: 100 first emails a day leaving 15 mailboxes from week 3, and each mailbox at 30 a day from week 6.
• It worked if: bounces stay under 2% every day, and you get at least 1 reply for every 100 first emails. Judge replies after 2,800 first emails, 4 weeks at 100 a day. Instantly's 2026 benchmark found an average reply rate of 3.43%, counting every reply, including "no". Book every "yes" as a discovery call.
• Common mistake: jumping from 0 to 30 a day on day 15 because the warm-up "is done". The jump itself looks like spam. Climb in 4 steps.

5. Check every day that your emails reach the inbox, and rest any mailbox that fails

Each morning, check three things for every mailbox: a test email lands in the inbox, bounces are under 2%, and the warm-up health score is above 90%. If a mailbox fails any of them, stop its cold email for 7 days and leave its warm-up on.

You cannot rely on Google Postmaster Tools for this. On 30 September 2025, Google removed its domain reputation score, and at your volume its dashboards may show no data at all. So use checks you can run yourself.

How.

1. Test send. Make one free personal Gmail account and one free Outlook.com account. Every morning, send one short, plain email from 3 different mailboxes to both, picking 3 new mailboxes each day so all 15 are tested every 5 days. Write down where each one lands: inbox, Promotions or spam.
2. Bounces. In Instantly's campaign analytics, check yesterday's bounces for each mailbox. Over 2% means the list is the problem: stop loading new addresses until they are checked again.
3. Health score. In Email Accounts, read the Health Score column. Under 90% means warm-up emails from that mailbox are landing in spam.
4. Rejections. Read any bounce that starts with 550 5.7 or says the message was blocked for policy or spam reasons. Gmail and Outlook send these when they refuse mail they do not trust. One of them is a warning for the whole domain: rest all 3 of its mailboxes.
5. Rest a mailbox. Set its Daily Campaign limit to 0 for 7 days, keep warm-up on, and move its share of the 100 to the other mailboxes, as long as none of them goes over this week's limit. Whatever still does not fit goes to LinkedIn and calls that week. After 7 days, restart it at 10 a day and climb again.

• Tool: a free Gmail account, a free Outlook.com account, and Instantly.
• Time: 10 minutes a day.
• You will have: one row a day in your sheet with where each test landed, yesterday's bounces and the health scores.
• It worked if: at least 9 of every 10 test emails land in the inbox (not spam), and no mailbox has a 550 5.7 bounce.
• Common mistake: rewriting the email when the real problem is that it lands in spam. If your test emails land in spam, fix the sending first. If they land in the inbox and you still get under 1 reply per 100, the problem is the words or the list: work on getting replies.

6. Every Sunday, count each mailbox and keep a spare domain warming

Every Sunday, add one row per mailbox to your sheet: emails sent, bounces, replies, health score and status. Then decide which mailboxes keep their limit, which rest, and whether to buy another spare domain.

How.

1. Fill in one row per mailbox for the week, and raise the daily limits to next week's step (step 4). Use your Google Sheet until it gets slow, then move to a CRM.
2. Keep a mailbox at its limit if its bounces were under 2%, its health score stayed above 90% and its test emails landed in the inbox.
3. Rest it for 7 days if it failed any check (step 5). Check that every rested mailbox is back at 10 a day once its 7 days are over.
4. Replace the domain if its mailboxes have failed two rests in a row. Stop cold email from it, keep warm-up running, and move its share to a spare domain.
5. Keep a spare warming. A new domain needs 2 weeks before its first cold email and 5 weeks to reach 30 a day. So on the Sunday before week 3, buy 1 spare domain, set up 3 mailboxes on it and start their warm-up. Keep one spare warming at all times, and buy another the week you start using one. It costs about $26 a month.
6. Count the replies and calls by the mailbox they came from, and by where each deal came from, not just the emails sent.

The decision after 2,800 first emails (4 weeks at 100 a day): if test emails land in the inbox and you get at least 1 reply per 100, keep the setup and work on the words. If test emails land in spam, rest the domains that fail and check SPF, DKIM, DMARC and your lead list before you send more. When a reply turns into a deal, move the conversation to your main address before you send a proposal. Once a month, look at all your channels in one marketing review.

• Tool: Google Sheets.
• Time: 20 minutes every Sunday.
• You will have: one row per mailbox for every week, and at least one spare domain warming.
• It worked if: every mailbox has a status for the week, and no week passes with fewer than 15 working mailboxes, counting spares that are ready.
• Common mistake: buying a new domain only after one fails. It then takes 5 weeks to reach full volume, and your 100 a day drops for all of that time.

Your email warm-up checklist for the next 6 weeks

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Step 1 · Buy 5 separate domains for cold email

• Buy 5 new domains close to your company name and send visitors from each to your main website.

Step 2 · Create 3 mailboxes on each domain and set up SPF, DKIM and DMARC

• Create 3 mailboxes on each domain with a real name, photo and signature.
• Add the SPF, DKIM and DMARC records for all 5 domains and check each mailbox with Show original.

Step 3 · Turn on warm-up and send only warm emails for 2 weeks

• Connect all 15 mailboxes to a warm-up tool and turn warm-up on.
• Every daySend 2 warm emails from each mailbox and the rest of your 100 messages on LinkedIn and by phone.
• Build your lead list to 1,400 named buyers with checked emails before day 15.

Step 4 · Start cold email at 10 a day per mailbox and reach 30 by week 6

• Set each mailbox's daily limit to 10, turn off tracking, and send text-only emails.
• Every daySend 100 personal first emails spread across your mailboxes.
• Every SundayRaise each mailbox's daily limit to the next step of the ramp.

Step 5 · Check every day that your emails reach the inbox

• Every daySend test emails from 3 mailboxes to your own Gmail and Outlook.com, and check bounces and health scores.
• Every dayRest any mailbox that failed a check for 7 days, with warm-up on.

Step 6 · Every Sunday, count each mailbox and keep a spare domain warming

• Every SundayFill in one row per mailbox and mark each one keep, rest or replace.
• Every SundayKeep at least 1 spare domain warming, and buy another when you use one.
• After 2,800 first emailsDecide whether low replies come from the sending or from the words and the list.

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