Why inbox providers hold back mail from a brand-new domain, how long it lasts, and how to warm one up at any volume.
Many senders are surprised that sending from a new domain brings its own challenges. As soon as you start sending at scale, inbox providers like Gmail and Microsoft slow down your mail until they've determined you're sending email people want to receive.
Whenever you're sending from a new domain, or one that hasn't sent much email, it's important to follow a few key practices, and it starts with understanding how inbox providers judge your mail.
Generally speaking, start sending at a low volume to people who expect your email, then increase it gradually as you build engagement.
Inbox providers decide where mail goes based on the sending domain's track record. They watch how recipients react: opens, replies, "Not spam" clicks, complaints, and bounces.
A brand-new domain has no track record. Spammers often register new domains and start sending right away, so filters treat unknown domains with caution and send more of their mail to spam until they build a history.
Authentication is important. Gmail, Yahoo, and Microsoft require SPF, DKIM, and DMARC from bulk senders. But it doesn't address the key problem: it proves the mail comes from you, not that recipients want it. Inbox providers want to see a history of sending email people want, and a new domain doesn't have that history yet.
This is temporary. Placement improves as positive signals build up.
There's no exact timeline. Some domains reach the inbox in a few days. Most get there within a week or so when they follow the practices below.
Microsoft (Outlook and Hotmail) and iCloud often take longer than Gmail to trust a new domain.
| Speeds it up | Slows it down |
|---|---|
| Mail people expect, such as signups and login codes | Announcements to people who never asked for them |
| Steady daily volume | Bursts, then days of silence |
| Recipients opening, replying, and clicking "Not spam" | Spam complaints |
| Recent, opted-in addresses | Old, bought, or scraped lists that bounce |
There's no universal limit. Each provider sets its own thresholds and adjusts them based on your sending history.
As a reference, Resend's warm-up guide starts a new domain at up to 150 emails on day 1 and up to 2,000 by day 7. Our calculator builds a day-by-day schedule for your target volume, on any provider.
Password resets and login codes can't wait for a schedule. You can still shape the rest:
Domains that send transactional mail only still need a warm-up. Expected mail builds reputation fast, but one burst, such as a launch day or a bot hammering your signup form, can still impact your trust with inboxes.
Each message carries more weight, so get the strongest signal you can from each one.
You might expect to track this in a reputation dashboard like Google Postmaster Tools, which shows how Gmail rates your domain. At low volume it won't help yet: Google only shows data on days when you send enough mail to Gmail. Until then, watch your bounces, complaints, and test emails to your own inboxes.
Providers track subdomains separately, but they also look at the root domain. A new subdomain like notifications.example.com on an established example.com starts with more trust than a brand-new domain.
Subdomains still need a warm-up, albeit a shorter one. Start with the mail people expect most and ramp up from there.
Throttling shows up as a temporary deferral, not a bounce. Gmail's response looks like this:
421 4.7.28 Gmail has detected an unusual rate of unsolicited email originating from your SPF domain example.com. To protect our users from spam, email sent from your domain has been temporarily rate limited.
It means you're sending faster than your history supports. Sending services retry deferred mail automatically, but messages expire if the deferral lasts too long.
Don't move the traffic to another domain to get around it, as that behavior can be flagged by inboxes and won't ultimately fix the problem.
Your warm-up is done when all of these are true:
Once the domain is warmed up, you don't need to repeat the warm-up as long as your volume stays steady. A big jump, such as 5 times your usual volume for Black Friday, needs a short ramp of its own.
Reputation fades when a domain stops sending. After a few months of silence, restart sending in small amounts and ramp up sending as with a new domain.
When warming up a domain, avoid shortcuts to the natural process described above. They promise to skip the wait, but most of them hurt your reputation.
| Shortcut | Verdict |
|---|---|
| Automated warm-up services | Avoid. They fake engagement between inboxes they control, and providers detect the pattern. |
| Emailing your own addresses | Fine as a test across providers. The volume is too small to warm a domain on its own. |
| Rotating domains or top-level domains | Avoid. Spreading volume thin across many domains is snowshoeing, a classic spam tactic. |
| Spreading mail across more IPs | Doesn't help. Providers weigh domain reputation more than IP reputation. |
Warm-up services also carry a lasting risk. Validity's Heatwave blocklist flags domains warmed with synthetic engagement, and that listing is permanent. Read more on warm-up services.
notifications.example.com and updates.example.com.Consistency and positive signals matter more than following a schedule to the letter. A warm-up table built for 50,000 emails a day won't fit a domain that sends 20.
Transactional mail mostly warms itself, because every message is expected. The risk is one burst. Get the domain live a few weeks before launch with real, low-volume traffic from your team and beta users.
If marketing launches at the same time, give it its own subdomain. That way, a spike there can't throttle your login codes.
notifications.example.com and updates.example.com, so early mistakes never touch your root domain. The free tier includes 3 domains.Does changing my From name or sender address hurt deliverability?
The From name has no impact, but changing the address can affect deliverability. Keep one address per type of mail, as Google's sender guidelines ask. Avoid no-reply@ and use an address someone reads, since replies are a positive signal.
Can I send email from a domain that has no website?
You can, but it's a missed signal. A website that loads on your domain helps providers and recipients trust your mail.
Does WHOIS privacy hurt deliverability?
No, hiding your registration details with WHOIS privacy has no effect on where your email lands.
Do I need to warm up a domain that only sends transactional email?
Yes. Transactional mail builds reputation fast because people expect it, but a sudden burst can still get you throttled. The warm-up guide covers it.
Why doesn't Google Postmaster Tools show data for my new domain?
Google hides Postmaster Tools data on days when your Gmail volume is too low. It fills in as your volume grows.