- Warmup builds sending history gradually so mailbox providers learn to trust a new IP or domain before you need full volume.
- Warm whatever is actually new: a dedicated IP, a domain, or both, which is the slowest case.
- Authentication, reverse DNS, a verified list and monitoring must all be in place before the first warmup send.
- Send to your most engaged recipients first and ramp only while bounce stays under 2% and complaints under 0.1%.
- A dedicated IP included with your plan, as on SendPulse SMTP Pro, Amazon SES or SendGrid, still starts cold and still needs a full warmup.
A brand-new domain that sends 5,000 emails on its first day looks, to a spam filter, exactly like a spammer spinning up fresh infrastructure. It does not matter how good your content is or how carefully you built your list. Without history, providers default to caution, and caution means throttling and the spam folder.
Warmup fixes this by introducing your new identity gradually: small volumes to people who will engage, growing on a steady schedule, proving good behavior before you scale. This guide covers what warmup actually builds, the setup you need before day one, day-by-day schedules for a new dedicated IP and a new domain, the metrics that tell you to speed up or back off, and the mistakes that force a restart.
Why warmup exists
Every new IP address and every new sending domain starts with a neutral to suspicious reputation. Gmail, Outlook, Yahoo and Apple have nothing to judge you by, so their filters throttle, defer or spam-folder unknown senders while they watch what happens.
The shape of your sending is itself a signal. Legitimate senders grow gradually as their audience grows. Spammers acquire new infrastructure and blast it immediately before it gets burned. Skip warmup and you reproduce the spammer’s pattern, and filters respond accordingly.
What warmup really builds is not volume tolerance but evidence. Opens, clicks, replies, low bounces, low complaints and recipients rescuing mail from spam are the signals that turn an unknown sender reputation into a good one.
IP warmup vs domain warmup
These are related but separate, and which one you need depends on what is new.
| Scenario | What to warm | Typical duration |
|---|---|---|
| New dedicated IP, established domain | IP only | 4 to 6 weeks |
| New domain, shared IP | Domain only (the shared IP is already warm) | 4 to 8 weeks |
| New domain and new dedicated IP | Both, slowest ramp | 6 to 12 weeks |
| New mailbox on an aged, healthy domain | Light warmup | 2 to 4 weeks |
| Returning after 90+ days of silence | Domain, and IP if dedicated | 2 to 6 weeks |
Providers track domain and IP reputation separately, and they increasingly weight the domain more. A shared IP arrives pre-warmed by other senders’ traffic, which is why IP warmup applies to dedicated IPs. Domain warmup applies whenever the domain itself is new or has gone quiet. If you are still deciding between the two IP models, our shared vs dedicated IP guide covers the trade-offs.
Other times you need to warm
- Migrating ESPs. A new provider nearly always means new IPs, even for a mature sender. See the ESP migration playbook.
- Long silence. After 90 or more days without sending, your engagement history is stale and providers treat you more cautiously.
- Big volume jumps. Adding a large new segment or doubling frequency should be ramped, not dropped in overnight.
Prerequisites: do these before day one
Warming a broken setup wastes the weeks you invest. Before the first send:
- Authenticate fully. Publish SPF, sign with DKIM (2048-bit keys) and set up DMARC with at least
p=noneand reporting. Check each with the SPF checker, DKIM checker and DMARC checker. Without authentication, providers cannot attribute your good behavior to your domain. - Set reverse DNS for dedicated IPs. The IP’s PTR record should resolve to a hostname on your domain, and that hostname should resolve back to the IP. Confirm with the reverse DNS checker.
- Use a custom tracking domain so your links sit on your own reputation from the start.
- Verify the list. A warmup that bounces in week one poisons the identity before trust exists. Run the list through a verifier such as ZeroBounce, NeverBounce or your platform’s built-in checker first. Our verification tools comparison can help you pick.
- Set up monitoring. Register the domain in Google Postmaster Tools and the IP in Microsoft SNDS now, so you have data from day one.
A typical DNS setup for a new sending subdomain looks like this (values illustrative):
news.example.com. TXT "v=spf1 include:_spf.youresp.example ~all"
sel1._domainkey.news.example.com. TXT "v=DKIM1; k=rsa; p=MIIBIjANBgkq..."
_dmarc.example.com. TXT "v=DMARC1; p=none; rua=mailto:dmarc@example.com"Warmup schedule for a new dedicated IP
This schedule assumes an established domain with good reputation, a verified list, and a target of around 50,000 emails per day. Scale the numbers to your own target, keeping the shape: roughly doubling at first, then growing by 30 to 50% per step once volumes are larger. Send on consecutive days; gaps slow the process.
| Day | Daily volume | Who to send to |
|---|---|---|
| 1 | 200 | Most engaged: clicked in the last 30 days |
| 2 | 400 | Same segment |
| 3 | 800 | Same segment |
| 4 | 1,500 | Engaged in the last 30 days |
| 5 | 2,500 | Engaged in the last 30 days |
| 6 | 3,500 | Engaged in the last 60 days |
| 7 | 5,000 | Engaged in the last 60 days |
| 8 to 9 | 7,000 | Engaged in the last 60 days |
| 10 to 11 | 10,000 | Engaged in the last 90 days |
| 12 to 14 | 14,000 | Engaged in the last 90 days |
| 15 to 17 | 20,000 | Engaged in the last 90 days |
| 18 to 21 | 28,000 | Engaged in the last 120 days |
| 22 to 25 | 38,000 | Active list |
| 26 to 30 | 50,000 | Full target list |
If your target is smaller, stop the ramp when you reach it. If it is larger, keep adding steps of 30 to 50% and hold two to three days at each level. For the first two weeks, spread each day’s volume evenly across major providers rather than letting one domain (often Gmail) absorb most of it.
Dedicated IPs that come with your plan
Several providers now bundle or sell dedicated IPs, and all of them start cold. SendPulse includes a dedicated IP on its SMTP Pro plan (around 100,000 emails per month), and you still need to follow a schedule like the one above before sending full volume through it. Amazon SES sells dedicated IPs as a monthly add-on and offers a managed option that warms automatically based on your traffic. SendGrid provides a dedicated IP on its Pro tier and has an automated warmup feature that shifts traffic gradually from shared to dedicated IPs. Automated warmup is convenient, but it only controls volume: you still decide who gets the mail, and early sends should go to engaged recipients.
Warmup schedule for a new domain
A new domain is slower than a new IP because providers weight domain reputation heavily and have nothing to go on. This schedule suits a new domain on a shared IP, or a new domain on a new dedicated IP if you stretch each stage by about 50%.
| Days | Daily volume | Who to send to | Notes |
|---|---|---|---|
| 1 to 3 | 50 | Customers and subscribers who clicked recently, plus internal seed addresses | Aim for replies where possible |
| 4 to 7 | 100 | Recent clickers | Check Postmaster Tools daily once data appears |
| 8 to 10 | 250 | Engaged in the last 30 days | |
| 11 to 14 | 500 | Engaged in the last 30 days | |
| 15 to 18 | 1,000 | Engaged in the last 60 days | Seed test Gmail and Outlook placement |
| 19 to 22 | 2,000 | Engaged in the last 60 days | |
| 23 to 26 | 4,000 | Engaged in the last 90 days | |
| 27 to 30 | 7,000 | Engaged in the last 90 days | |
| 31 to 35 | 12,000 | Active list | Hold if any metric wobbles |
| 36 to 42 | 20,000 | Active list | |
| 43+ | Grow 25 to 50% per step to target | Full target list | Keep stepping until you reach steady state |
For a single new mailbox used for one-to-one sales email, the numbers are far smaller: start around 10 to 15 per day, move to 20 to 30 in the second half of week one, 40 to 70 in week two, and 80 to 150 in weeks three and four if replies and placement stay healthy.
Send to your best recipients first
Volume is only half of warmup. Who receives the first messages matters just as much. Early traffic should go to the people most likely to open, click and reply, because those signals teach providers that your mail is wanted.
The order that works: start with recent clickers and customers who buy, then widen to less engaged segments as reputation builds. Never start with an old, cold or unengaged segment. You would be teaching filters the wrong lesson at the exact moment they form their first impression. Save re-engagement campaigns until warmup is complete.
Metrics to watch during warmup
Warmup is a feedback loop, not a fixed script. Check these at every step:
| Metric | Healthy | Pause and investigate | Stop |
|---|---|---|---|
| Bounce rate | Under 1% | 1 to 2% | Over 2% |
| Spam complaint rate | Under 0.1% | 0.1 to 0.3% | Over 0.3% |
| Deferrals (421, 4.7.x) | Rare | Rising day over day | Widespread at one provider |
| Postmaster domain reputation | High or Medium | Drops a level | Low or Bad |
| Inbox placement (seed tests) | Mostly inbox | Mixed at one provider | Mostly spam |
Deferral codes like 421 and 4.7.0 mean the receiver wants you to slow down. Respect them. Your platform will retry, but pushing more volume on top teaches the filter that you ignore its signals.
Automated warmup services: use with caution
Warmup services exchange automated mail between member inboxes to generate opens, replies and “not spam” actions. They are popular in cold outreach and can build a baseline in the first weeks, but there are real caveats. Google and Microsoft work to detect these networks, so the value of synthetic engagement is shrinking and carries some risk. More fundamentally, it teaches filters nothing about your actual audience.
For marketing and transactional infrastructure, skip them and warm with real engaged subscribers. If you do use one for cold outreach, treat it as a supplement and let real traffic carry more weight as the ramp progresses.
Mistakes that reset your progress
- Sending production volume too early. A single premature spike can undo weeks of work.
- Inconsistent sending. Gaps and erratic volume teach providers nothing useful. Send every day on a predictable schedule.
- Starting with a dirty list. Week-one bounces damage the identity before trust exists.
- Skipping authentication. Warmup without SPF, DKIM and DMARC is far less effective and, for bulk senders, breaks the Gmail and Yahoo requirements.
- Warming with unengaged recipients. Volume without positive signals builds nothing.
- Pushing through a problem instead of pausing when metrics degrade.
How to know you are done
You are warm when your target daily volume goes out without significant deferrals, bounces and complaints stay low, engagement is steady, and seed tests show consistent inbox placement at the major providers. If those conditions are not consistently true, extend the warmup at the current level instead of moving on hope.
After that, the job shifts from building reputation to keeping it: clean lists, steady volume, fast unsubscribe handling and regular checks with the sender reputation checker. Reputation fades when you go quiet, so a warm identity needs consistent sending to stay warm. Treat warmup as the opening chapter of an ongoing discipline, and fold it into your wider deliverability practice.
Frequently asked questions
How long does email warmup take?
It depends on what is new. A new mailbox on an established, healthy domain usually needs two to four weeks. A new domain on a shared IP needs roughly four to eight weeks. A new domain on a new dedicated IP needs six to twelve weeks, because both identities start from zero. Extend any schedule if bounces, complaints or placement are not consistently healthy.
Do I need to warm up a shared IP?
No. A shared IP already carries traffic from other senders, so its IP reputation exists. You still need to warm your domain if it is new or has been quiet, because providers track domain reputation separately and weight it heavily. On a shared IP, follow the domain schedule and focus on sending to engaged recipients first.
What happens if I skip warmup?
Providers see an unknown identity suddenly sending volume, which is exactly how spammers use fresh infrastructure. They respond with deferrals such as 421 or 4.7.0 codes, spam folder placement and sometimes outright blocks. A large share of early mail can land in spam, and the damage to a new domain is much harder to repair than the few weeks warmup would have taken.
Do automated warmup services work?
They can create a baseline of opens and replies in the first weeks, but Google and Microsoft actively look for warmup networks, and synthetic engagement says nothing about your real audience. For marketing and transactional mail, warm with real engaged subscribers instead. If you use a service for cold outreach, treat it as a supplement and let real traffic take over quickly.
Do I need to warm up again after switching ESPs?
Usually yes. A new ESP almost always means new sending IPs with no history, even if your domain and list are mature. Your domain reputation carries over, which shortens the process, but you should still ramp volume over a few weeks. The same applies after 90 or more days of silence, or when adding a large new segment to your sends.