How to warm up a cold email domain.

1. Why warm-up matters

Gmail, Outlook and other mailbox providers decide where your email lands partly on the reputation of the sending domain and mailbox. A domain registered last week has no reputation at all. If it suddenly sends hundreds of emails to strangers, that pattern looks like spam, and the provider reacts accordingly: messages go to the spam folder, get delayed, or are rejected outright.

Warming up means building that reputation on purpose: authenticating the domain properly, starting with very low volume, and raising it slowly while recipients open, reply and don't complain. There is no shortcut. A domain that is warmed carefully over several weeks is far easier to keep healthy than one you have to rescue after it is burned.

2. Use a separate sending domain

Don't send cold email from your main company domain. If a campaign goes badly, the damage lands on the domain your invoices, password resets and customer support also use. Register one or more look-alike domains for outreach instead.

• Pick something close to your brand. If you are acme.com, options like tryacme.com, acmehq.com or getacme.com look legitimate to recipients.
• Avoid odd top-level domains that tend to be associated with spam. A .com or your country's usual domain is the safe choice.
• Redirect the domain to your main website, so anyone who types it in lands somewhere real.
• Give it time. Many teams let a new domain sit for a week or two while they set up DNS and warm-up, rather than sending on day one.
• Plan for more than one. If you need meaningful volume, spread it over several domains and mailboxes instead of pushing one hard.

3. SPF, DKIM and DMARC

These three DNS records let receiving servers check that your email really comes from you. Google's sender guidelines require bulk senders to Gmail to have SPF, DKIM and DMARC in place, and missing authentication is one of the simplest reasons for poor inbox placement. Set all three before you send anything.

Practical notes

• A domain may have only one SPF record. If you add a sending tool, merge its include: into the existing record instead of adding a second one.
• Start DMARC at p=none to collect reports, then move to quarantine once you've confirmed everything legitimate passes.
• Make sure the domain in the visible From address aligns with the domain that SPF or DKIM authenticates. Sending from tryacme.com through a tool that signs as a different domain can fail DMARC.
• Test with a free header checker, or send to your own Gmail account and use “Show original” to confirm SPF, DKIM and DMARC all show PASS.

4. Set up the mailboxes

Create real mailboxes on the new domain, on a mainstream provider such as Google Workspace or Microsoft 365, and make them look like the real people they are.

• Use a person's name for the address ([email protected]) and the display name, not sales@.
• Add a profile photo and a plain signature with name, title and your main website.
• Keep the number of mailboxes per domain modest, and the number of cold emails per mailbox modest too. Spreading volume is safer than concentrating it.
• Use the mailbox normally for the first days: send a few real emails to colleagues and partners, and reply to what you receive. Many teams also use a warm-up service that exchanges emails between mailboxes to build early engagement.

5. The warm-up schedule

The ramp below is a conservative example for one new mailbox. It isn't an official limit from any provider, and the right pace depends on your audience and results. If replies are healthy and bounces stay low, keep going; if anything in section 8 goes wrong, hold or step back a week.

Worked example

You want to reach about 600 prospects a week. At 30 cold emails per mailbox per weekday, one mailbox sends 150 a week, so you'd need four warmed mailboxes, for example two each on tryacme.com and acmehq.com. Set them up in the same week, follow the ramp together, and you reach that pace around week five instead of overloading one mailbox from day one.

6. Send to verified emails only

Bounces are the fastest way to damage a new domain. An address that doesn't exist produces a hard bounce, and a high share of hard bounces tells providers you are mailing a list you didn't build carefully. During warm-up, when your reputation is thinnest, every bounce counts more.

• Verify every address before it goes into a campaign. Lists go stale as people change jobs, so verify close to the send date.
• Never send to guessed addresses. A pattern like [email protected] is a guess until a verification check confirms it.
• Drop role addresses from early sends if your audience is people. Addresses like info@ are fine for some campaigns but often go to shared inboxes with lower engagement.
• Remove bounces immediately and never retry a hard bounce.

This is where QuickExtract fits. Every verified person email it returns has passed three checks: format and domain, mailbox, and a dedicated catch-all verification. An address that fails any pass is dropped, and you aren't charged for it. If you already have a list from somewhere else, you can run it through the same verification with the email verifier, using the same credits. Company emails QuickExtract finds on websites are free; run them through the verifier too if you plan to mail them from a new domain.

7. The catch-all risk

Some company mail servers accept every address at their domain, real or not. On those “catch-all” domains a standard mailbox check sees “accepted” for any guess, so many verifiers can only label the address unknown or risky. Send to a batch of those and some will bounce later, or quietly vanish without a reply.

During warm-up, either leave unconfirmed catch-all addresses out entirely, or only send them once your domain is established and in small, separate batches. QuickExtract's third pass is a dedicated catch-all verification, so you keep the real addresses on those domains and drop the guesses. The full explanation is in Catch-all emails explained.

8. Bounce and complaint targets

Inbox providers don't publish bounce thresholds, so treat these as working rules of thumb rather than official numbers. The spam-rate figures come from Google's sender guidelines.

Set up Google Postmaster Tools for each sending domain so you can see domain reputation and spam rate for mail delivered to Gmail users.

9. Content tips

• Plain text, short. A few sentences, no images, no attachments, no HTML templates.
• Few or no links in the first email, and never link shorteners. If you link, link to your own main domain.
• Turn off open tracking during warm-up if your tool allows it; tracking pixels and tracked links add signals filters look at.
• Personalize for real. A first name alone isn't personalization. A line about the company, their role, or why you're writing now earns replies, and replies are what build reputation.
• Handle missing first names. If a row only has a company inbox like info@, a fallback such as {{firstName|there}} renders “Hi there” instead of “Hi ,”.
• Make opting out easy. Offer a simple way to opt out and honor it at once, as anti-spam laws such as CAN-SPAM require.
• Vary your wording across sequences instead of sending one identical message thousands of times.

10. Monitor and adjust

Warm-up doesn't end on a fixed date. Keep an eye on the same few signals every week:

1. Check bounces after each campaign and remove them.
2. Review spam rate and domain reputation in Postmaster Tools.
3. Send a test to seed accounts you control on Gmail and Outlook and see where it lands.
4. If placement drops, cut volume by half for a week, re-verify the next list, and simplify the copy before ramping again.

A domain that keeps getting clean lists, steady volume and real replies tends to stay healthy. Most deliverability problems trace back to one of those three slipping.