Email warm-up is the process of gradually increasing how much mail you send from a new domain or IP address so mailbox providers can build a reputation for it. You start with small daily volumes sent to your most engaged recipients, then raise volume step by step while watching bounces, deferrals, and complaints. Industry guidance puts a typical warm-up at roughly two to six weeks, depending on the provider and your volume.

This guide focuses on running the warm-up itself: the schedule, who to mail, what to watch, and when to stop and back off. If you’re still setting up DNS and accounts for a brand-new domain, start with our checklist for sending from a new domain, then come back here.

Why email warm-up is necessary

Mailbox providers judge mail partly by the history of the domain and IP it came from. A new sender has no history, and the M3AAWG Sender Best Common Practices (version 4.0, August 2026) put it bluntly: a new domain’s reputation usually starts as unknown, which is treated much like bad, because there’s nothing to judge it by. The same document warns that an established domain that has never sent mail and suddenly starts sending large volumes can be a problem too.

Providers say the same thing in their own guidelines. Google’s sender guidelines ask senders to:

Increase volume slowly, and more slowly the larger your target volume is
Send at a consistent rate instead of in bursts
Start with your most engaged users
Reduce volume when bounces or deferrals go up, and ramp back up once errors drop

Skipping warm-up doesn’t just risk the spam folder. It can lead to throttling (421 or 451 temporary failures) or outright blocks that take time to undo.

Domain warm-up vs. IP warm-up

You may need to warm up one, the other, or both.

Situation	Warm up the domain?	Warm up the IP?
New domain, ESP shared IP pool	Yes	No, the pool is already warm
New subdomain of an established domain	Yes, recommended	Depends on IP
Existing domain, new dedicated IP	Usually not, but ramp volume	Yes
New domain, new dedicated IP	Yes	Yes, both at once
Moving ESPs, same domain, new shared pool	Light ramp recommended	No

M3AAWG recommends warming a new subdomain even when the parent organizational domain already has a good reputation. For the differences between the two reputations, see domain reputation vs IP reputation.

How long does email warm-up take?

There’s no universal number, but primary sources give a useful range:

Amazon SES says that for dedicated IPs, some providers will establish a positive reputation in around two weeks, while others may take up to six weeks. Its automatic warm-up for standard dedicated IPs steadily raises the warm-up percentage over 45 days.
M3AAWG suggests considering six weeks as an average for domain warm-up.

Plan for about six weeks to reach full volume if your target is large. Smaller targets may get there faster.

A sample email warm-up schedule

No mailbox provider publishes an official schedule, so treat the table below as an example of the shape a warm-up should take, not a rule. It assumes a target of roughly 50,000 messages a day and daily sending. Adjust the steps to your own target and slow down whenever the signals in the next section go bad.

Week	Daily volume (example)	Who to send to
1	A few hundred, rising each day	Opened or clicked in the last 30 days
2	Low thousands	Engaged in the last 30 to 60 days
3	Several thousand	Engaged in the last 90 days
4	10,000 to 20,000	Engaged in the last 90 to 120 days, new confirmed signups
5	20,000 to 35,000	Broader active list
6	Up to target	Full list, minus long-term inactives

Some practical rules to go with the table:

Grow in steps, not jumps. Raise volume only after a day or two of clean results at the current level.
Spread sends across the day. M3AAWG recommends not sending your whole daily batch at once.
Send on a regular schedule. Regular daily or near-daily sending builds history faster than one weekly blast. Google notes that daily senders can ramp faster than weekly senders.
Watch each provider separately. Gmail may be happy while Outlook.com is deferring you. Slow down only where it’s needed if your platform allows per-domain throttling.
Keep it up afterward. AWS recommends sending around 1,000 emails a day to each provider you care about from each warmed dedicated IP to keep its reputation, and avoiding a big volume jump right after warm-up ends.

Who to email first during warm-up

The recipients you pick during the first two weeks matter more than the volume.

Start with your most engaged people. Recent openers, clickers, buyers, and active users are least likely to complain and most likely to interact.
Use confirmed, recent signups. New double opt-in subscribers are ideal.
Leave risky segments for last, or out entirely. Old imports, contacts who haven’t engaged in a year, and anything from a list you didn’t build yourself should not go anywhere near a warm-up.
Verify before you send. A warm-up with a high bounce rate teaches providers the wrong thing about you. Run imported or older segments through our free email verifier to catch malformed addresses, domains without MX records, disposable domains, role addresses, and typo domains. It doesn’t connect to the recipient’s mailbox, so some invalid mailboxes will still slip through, but it removes the easy failures before they cost you.

What to monitor during the warm-up

Check these after every send, not once a week.

Bounces and deferrals in your logs

Your SMTP responses are the earliest warning. Watch for:

421 4.7.0 or similar “try again later” responses, which mean the provider is throttling you
Gmail’s 421 4.7.28 rate-limit response. Google’s guidelines say to pause for at least 10 minutes, then resume with a single connection and add connections one at a time
550 5.7.1 policy rejections, which can mean a block or blocklist listing
Rising 550 5.1.1 User unknown hard bounces, which point to list quality

Spam complaint rate

Google wants the user-reported spam rate below 0.1% and never at 0.3% or higher, per its sender FAQ. A complaint spike during warm-up is a reason to stop and look at who you mailed.

Engagement by provider

M3AAWG suggests watching opens and clicks: drops may mean your mail is going to junk. Big unexpected spikes in clicks can mean corporate security scanners are opening links, which is worth noting but not necessarily bad.

Postmaster and feedback tools

Set up Google Postmaster Tools, Microsoft SNDS if you have your own IPs, and Yahoo’s Complaint Feedback Loop before the first send, so data is flowing when you need it.

When to slow down or stop

Use simple rules so you don’t argue with yourself mid-warm-up:

Deferrals rising at a provider: hold volume at that provider flat until they clear, then resume.
Complaints rising: stop expanding the audience and go back to your most engaged segment.
Hard bounces rising: stop, find the segment responsible, and clean it before continuing.
Blocks or blocklist listings: pause that stream entirely, investigate, and request delisting only after fixing the cause. See email blacklists explained.

What about automated warm-up tools?

Some services “warm” a mailbox by exchanging messages with a network of other accounts that automatically open, reply, and rescue each other’s mail from spam. M3AAWG states that artificial warming practices are not recommended and may be illegal. Fake engagement doesn’t teach providers that your real recipients want your mail, and when real sending starts the reputation you built may not hold. The reliable way to warm a domain is real mail to real people who asked for it.

For cold outreach specifically, also see cold email sending limits and secondary domains for cold email.

FAQ

How long does email warm-up take for a new domain?

Plan for about two to six weeks. AWS reports that providers take anywhere from around two weeks to up to six weeks to establish reputation for a new dedicated IP, and M3AAWG suggests six weeks as an average for domains. Larger target volumes need longer ramps.

Do I need to warm up if I use a shared IP from my ESP?

The IP is already warm, but your domain may not be. If your From: and DKIM domain is new or has never sent bulk mail, ramp up volume anyway, because mailbox providers track domain reputation separately from IP reputation.

Can I warm up a domain by sending to my own team?

Sending only to internal or seed addresses doesn’t create meaningful reputation with Gmail, Yahoo, or Microsoft, because those providers learn from how their own users react. Real warm-up needs real opted-in recipients at those providers, starting with the most engaged.

What happens if I skip email warm-up?

You’ll likely see throttling, higher spam-folder placement, and possibly blocks, especially at large providers. Recovering from a bad start usually takes longer than warming up properly would have.

Should I warm up a new subdomain of a domain I already use?

Yes. M3AAWG recommends warming a new subdomain even if the parent domain has a good reputation. The ramp can often be shorter, but don’t jump straight to full volume.

Email Warm-Up: How to Warm Up a New Domain or IP Safely