Imagine a stranger suddenly knocking on ten thousand doors at once. People would be suspicious. Inbox providers think the same way. When a new domain, or a domain using a new sending tool, suddenly sends thousands of emails, it looks like spam, even if it is not.
Warming up means increasing how many emails you send slowly, so inbox providers can see that people want your emails before you send at full volume.
When you need to warm up
- You bought a new domain and are sending from it for the first time.
- You moved to a new email marketing tool.
- You are sending from a new subdomain, such as news.yourbrand.com.
- You have not emailed your list in many months.
- You are getting a dedicated IP address from your email provider.
If you have been sending steadily from the same domain and tool for a while, you do not need to warm up.
Before you start
Warming up only works if the basics are in place:
- Your domain is authenticated with SPF, DKIM and DMARC in your email tool.
- Your from address uses your own domain.
- Your list is made of people who opted in. Remove anyone who bounced before.
Warming up a messy list does not fix it. It just spreads the damage out over a few weeks.
Start with your best subscribers
The secret to warming up is sending your first emails to the people most likely to open, click and reply. These positive signals tell inbox providers your emails are wanted.
Good first groups include:
- People who joined your list recently.
- People who clicked in your last few emails.
- Customers who bought recently.
Save less active subscribers for later in the warm up.
A simple warm up plan
There is no single perfect schedule. Your email tool may give its own advice, which you should follow. For a small business list, a gentle plan might look like this:
- Week 1: send to a few hundred of your most engaged subscribers, a few times across the week.
- Week 2: roughly double the size of each send, still focusing on engaged people.
- Week 3: double again and start including people who have been active in the last few months.
- Week 4 onwards: move up to your full list of active subscribers.
If your list is small, a few hundred people in total, you can usually move faster. If it is very large, take longer.
Watch your numbers after every send
Check these after each send before you increase volume:
- Bounces: if many emails bounce, stop and clean your list.
- Spam complaints: keep them below 0.1 percent. If they rise, slow down.
- Clicks and replies: healthy engagement means you can keep growing.
- Where emails land: send to test accounts on Gmail, Outlook and Yahoo and check inbox versus spam.
If things go wrong, step back to the previous volume for a few sends before trying again.
Encourage engagement during warm up
- Write emails people genuinely want, such as your best tips or a useful update.
- Ask a simple question and invite replies. Replies are a strong positive signal.
- Keep emails clean with a few clear links.
Do not buy a warm up shortcut
Some services promise to warm up your domain automatically using fake engagement. Inbox providers are getting better at spotting this, and it does nothing for your real reputation with real subscribers. The honest way is slower but lasts.
The short version
Set up your domain properly, start with your most engaged people, grow your send sizes slowly and watch your numbers. In a few weeks, inbox providers will know who you are and your emails will be treated like the welcome guests they are.
Mailbox providers update their filters and requirements regularly. This guide was last reviewed on May 12, 2026. Spotted something out of date? Tell us.