Email warm up is the process of building a sending history for a new email address or domain by starting with a small number of real, wanted emails and raising the volume slowly over a few weeks. Inbox providers like Gmail and Outlook judge you on how people react to your mail. A brand new domain has no track record, so if it suddenly sends hundreds of messages a day, the safest move for them is to junk or block it.
Warm-up gives them a reason to trust you. Done properly, it’s the difference between outreach that lands in the inbox and a domain that’s burned before your first campaign gets going.
What email warm up actually does
Mailbox providers score every sender. That reputation is tied to your sending domain and, if you use one, your dedicated IP address. They look at signals like:
- How many people open, reply to, or move your emails out of spam
- How many people mark your emails as spam
- How many messages bounce because the address doesn’t exist
- Whether your authentication (SPF, DKIM and DMARC) passes
- Whether your volume is steady or jumps around without warning
A new domain has none of this history. Warm-up builds it on purpose, a little at a time, so the first big signal providers see is a positive one.
Who needs to warm up an email address?
You should plan a warm-up if any of these apply:
- You’ve bought a new domain for cold outreach or sales emails
- You’re moving your newsletter or marketing email to a new provider or a dedicated IP
- An inbox has been sitting unused for months and you want to start sending again
- Your deliverability has dropped and you’re rebuilding after a spam problem
If you only send normal one-to-one business email from an established domain, you don’t need a formal warm-up. Just get your authentication right.
Set up authentication before you send anything
Warm-up won’t save a domain that fails authentication. Since 2024, Gmail and Yahoo have required bulk senders to authenticate their mail, and Microsoft added similar rules for Outlook.com, Hotmail and Live addresses in May 2025. Put these in place first:
- SPF. A DNS record listing the servers allowed to send for your domain.
- DKIM. A digital signature that proves the message wasn’t changed in transit. Your email provider gives you the record to add.
- DMARC. A policy that tells receivers what to do when SPF or DKIM fails. Start with
p=noneso you can monitor reports, then tighten it once everything passes. - Matching domains. The domain in your From address should align with the domain that passes SPF or DKIM.
- Reverse DNS (PTR). If you run your own sending IP, it needs a valid PTR record. Google Workspace and Microsoft 365 handle this for you.
- One-click unsubscribe. Required for marketing and promotional mail sent in bulk.
The thresholds are worth knowing. Google treats anyone sending close to 5,000 messages a day to personal Gmail accounts as a bulk sender, and that status doesn’t expire. Microsoft’s rules apply to domains sending more than 5,000 emails a day to its consumer inboxes, and mail that fails is now rejected outright rather than sent to junk. You can read the details in Google’s email sender guidelines FAQ and Microsoft’s announcement for high-volume senders.
How to warm up a new email domain, step by step
- Use a separate domain for cold outreach. Many teams send outreach from a close variation of their main domain so a mistake doesn’t hurt the domain their invoices and customer emails rely on. Point the new domain’s website to your main site so it doesn’t look abandoned.
- Set up the mailbox like a real person uses it. Add a name, a profile photo and a simple signature. Send and reply to a few normal emails with colleagues and contacts.
- Let the domain age a little. If you can, give a brand new domain a week or two of light, normal use before outreach starts.
- Start with people who want to hear from you. Your first sends should go to existing contacts, customers or partners who are likely to open and reply. Replies are one of the strongest positive signals you can get.
- Raise the volume gradually. Increase your daily sends in small steps, and only move up when the numbers look healthy. The table below is a cautious example for one inbox, not a rule from any provider.
- Clean every list before you use it. Verify addresses, remove role accounts you don’t need and never buy lists. Bounces early in a warm-up do real damage.
- Write emails people will answer. Plain text, a relevant reason for writing, one clear question, no link-heavy templates or attachments while you’re still building trust.
- Keep sending steadily. Reputation fades if you stop. Spread sends through the working day instead of firing them all at once.
Example warm-up schedule for one new inbox
| Week | Emails per day | Who to send to |
|---|---|---|
| Week 1 | 5 to 10 | Colleagues, existing contacts, people who know you |
| Week 2 | 10 to 20 | Warm contacts and a small, verified prospect list |
| Week 3 | 20 to 30 | Verified prospects, with replies coming in |
| Week 4 | 30 to 50 | Normal outreach, if spam complaints and bounces stay low |
If a week goes badly, with more bounces, spam placement or complaints, hold the volume where it is or drop back a step. Don’t push through problems. For larger programs, it’s usually safer to add more inboxes than to push one inbox to high daily numbers.
How long does email warm up take?
For a single inbox on a new domain, plan on roughly two to four weeks of steady sending before you run outreach at your normal pace. A dedicated IP for marketing email or a large list migration can take longer, because you’re building trust for far more volume. There’s no official number from Gmail or Microsoft. The real answer is: until your metrics stay healthy at the volume you need.
Do automated warm-up tools work?
Tools like Instantly, Smartlead and Warmy run automated warm-up. They connect your inbox to a network of other inboxes that send each other messages, open them, reply and pull them out of spam. That creates positive engagement while your real volume is still low.
They can help, especially for teams running several outreach inboxes. Keep their limits in mind:
- They don’t fix bad lists, poor targeting or emails nobody wants.
- Providers can spot patterns, and engagement from a warm-up network isn’t the same as replies from real prospects.
- They’re no replacement for correct SPF, DKIM and DMARC.
My view: use a tool as support if you want one, but treat real conversations with real contacts as the main event.
How to tell if your warm-up is working
- Spam complaint rate. Google asks senders to keep their user-reported spam rate below 0.1% and never let it reach 0.3%. You can check yours in Google Postmaster Tools once you send enough volume to Gmail.
- Bounce rate. Hard bounces should be rare. If they aren’t, your list needs cleaning before you send more.
- Inbox placement. Send test emails to your own Gmail and Outlook accounts and see where they land.
- Replies. A healthy outreach inbox gets responses, even if some are a polite no.
- Authentication results. Your DMARC reports should show SPF and DKIM passing for the mail you send.
Common email warm up mistakes
- Sending a full campaign from a domain that’s a few days old
- Skipping DMARC or leaving SPF records broken after switching providers
- Using unverified or bought lists
- Jumping volume overnight because the first week went well
- Stopping all sends for weeks, then restarting at full volume
- Stuffing early emails with links, images, tracking and attachments
Email warm up and link building outreach
Most of my outreach email goes to editors, journalists and site owners, so deliverability matters directly to SEO results. If your pitch never reaches the inbox, it doesn’t matter how good it is. A warmed-up domain is the base for tactics like skyscraper link building and pitching journalist requests, and it’s part of how I run link building campaigns for clients.
FAQ
What is email warm up?
It’s the practice of building a good sending reputation for a new email address, domain or IP by starting with low volume to engaged recipients and increasing it gradually, so inbox providers learn to trust your mail.
Do I need to warm up a Gmail or Outlook address?
If it’s a new Google Workspace or Microsoft 365 inbox on a new domain and you plan to send outreach or marketing email, yes. If you only send everyday one-to-one email, you don’t need a formal warm-up.
How many emails should I send per day when warming up?
Start small, around 5 to 10 a day to people who know you, and increase in steps each week while bounces and complaints stay low. No provider publishes an official number, so let your metrics guide you.
Can I skip warm-up if I set up SPF, DKIM and DMARC?
No. Authentication proves who you are. Warm-up proves people want your mail. You need both.
Does email warm up ever stop?
The ramp-up phase ends, but reputation has to be maintained. Keep sending steadily, keep lists clean and keep complaint rates low.
Need outreach that reaches the inbox?
If you’re planning outreach as part of a wider SEO push, see the results in my case studies, scope your project with the SEO cost calculator, or get in touch to talk it through.