You set up a new domain for your business email or newsletters, configure everything correctly, send your first campaign, and most of it lands in spam. Nothing is broken. Mailbox providers simply do not trust senders they have never seen before. Email warm-up is the process of building that trust gradually, so that by the time you send at full volume, your domain and servers have a history of mail that people want.
Why new senders are treated with suspicion
Gmail, Outlook.com, Yahoo and corporate filters score every message partly on the reputation of the sending domain and the IP address it comes from. Reputation is built from history: how much mail you send, how many recipients open, reply or mark it as spam, and how many addresses bounce.
A brand-new domain or IP has no history. Spammers know this too, which is why they constantly register fresh domains and blast large volumes from them before they are blocked. A new sender that suddenly sends thousands of messages looks exactly like that pattern. A new sender that starts small and grows steadily looks like a real business.
Domain warm-up versus IP warm-up
- Domain reputation follows your domain wherever you send from. Every new sending domain needs warming, even if you use a well-known email service.
- IP reputation matters when you send from a dedicated IP address, such as your own mail server or a dedicated IP from an email service provider. On shared IPs the provider's existing reputation covers this part for you.
Most small and mid-sized businesses on Google Workspace, Microsoft 365 or a shared newsletter service only need to warm the domain. Companies sending large volumes from dedicated IPs need to warm both.
Before you send anything
Warm-up cannot fix a technical setup that fails authentication. First make sure:
- SPF lists every service that sends for the domain.
- DKIM signs with your own domain, not only the provider's.
- DMARC is published, starting with
p=noneand a reporting address. - Reverse DNS for a dedicated IP points to a hostname that resolves back to the same IP.
- The domain has a working website. Filters look at whether links lead somewhere legitimate.
You can confirm the first three with the SPF, DKIM and DMARC checker.
A sample warm-up schedule
The exact numbers depend on your final volume, but the shape is always the same: start with your most engaged recipients, increase gradually, and pause if problems appear. This schedule suits a business aiming for around 10,000 messages a day:
| Days | Messages per day | Who to send to |
|---|---|---|
| 1–3 | 50–100 | Colleagues, existing customers who reply often |
| 4–7 | 200–500 | Customers active in the last 30 days |
| 8–14 | 1,000–2,000 | Customers active in the last 90 days |
| 15–21 | 3,000–5,000 | Engaged subscribers from the last six months |
| 22–30 | Up to 10,000 | Your normal list, still excluding long-inactive addresses |
Roughly doubling every few days works well. If you only send a few hundred emails a day in total, the whole process may take a week or two of normal, careful use.
What helps reputation during warm-up
- Replies. A reply is one of the strongest positive signals. Personal one-to-one email from the new domain helps a lot.
- Consistent volume. Send most days rather than in occasional bursts.
- Clean lists. Remove invalid addresses before you start; a burst of hard bounces early on is very damaging.
- Easy unsubscribe. Include a one-click unsubscribe link in bulk mail. A recipient who unsubscribes is far better for you than one who reports spam.
- Plain, useful content. Avoid link shorteners, image-only messages and heavy tracking while the domain is new.
Watching the results
Do not warm up blind. Keep an eye on:
- Google Postmaster Tools, which shows your domain and IP reputation and spam complaint rate for Gmail recipients.
- Microsoft SNDS for dedicated IPs sending to Outlook.com.
- DMARC aggregate reports, to catch any service sending without proper authentication.
- Bounces and complaints in your sending platform. Keep complaints under 0.1% and well away from 0.3%.
If complaint or bounce rates rise, stop increasing volume, go back a step, and look at which part of the list caused it.
About automated warm-up services
Some tools promise to warm a domain automatically by exchanging messages within a network of mailboxes that open and reply to each other. They can show early positive signals, but providers increasingly recognise these patterns, and the reputation they create does not reflect how your real recipients behave. Treat them as a supplement at most. Real engagement from real customers is what lasts.
Key takeaways
- New domains and IPs have no reputation, so large sudden volumes look like spam.
- Get SPF, DKIM, DMARC and reverse DNS right before you start.
- Start with your most engaged recipients and increase volume gradually over two to four weeks.
- Monitor reputation, bounces and complaints, and slow down at the first sign of trouble.