Don’t skip the warm-up: A practical guide to IP warming

TL;DR

Brands that begin sending emails on new IPs without carrying out an effective IP warming process run the risk of undermining their overall email deliverability efforts, reducing the impact of this key channel. This piece explores key considerations for a successful IP warm-up and gives marketers guidance on how to avoid common pitfalls.

Key takeaways

• IP warming exists to allow brands to demonstrate to inbox providers that the marketing emails they send are wanted, valuable, and relevant to the people receiving them, supporting stronger sender reputations
• To develop an IP warming strategy, experts recommend reviewing your organization’s expected sending volume, audience engagement, and long-term growth plans to build a bespoke sending schedule
• One of the biggest challenges with IP warming isn’t the technical aspects of the process, but rather internal pressures from executives and other stakeholders who don’t understand the potential ramifications that come with neglecting or rushing a warm-up

Imagine moving to a new neighborhood and, on your first day, dropping flyers in every mailbox on the block. Even if your flyers are totally legitimate—like a pizza menu, a lost cat notice, whatever—you’d probably get some side-eye. You’re new. Nobody knows you. You haven’t built any goodwill or reputation yet.

That’s more or less how inbox providers like Gmail, Microsoft , Yahoo and others see it when a company begins using a brand new sending IP. You’re an unknown quantity, and they’re not going to give your email the benefit of the doubt right away. IP warming is the process of building that goodwill deliberately, methodically, and with a healthy amount of patience.

Why IP warming exists

Inbox providers use IP reputation as one of their primary signals for email filtering decisions. A fresh IP has no history, no sends, no engagement data, no track record. To a mailbox provider, that’s suspicious. Spammers routinely spin up new IPs to dodge blocks, so mailbox providers are understandably skeptical of new senders who suddenly want to send millions of emails.

The warm-up process gives providers time to observe your sending behavior and see that real people are engaging with your email (e.g. opening it, clicking it, not marking it as spam). That engagement history builds your reputation score, which in turn determines whether future messages land in the inbox or get quietly dropped into the spam folder.

What happens when you skip IP warming

The short answer: Not great for deliverability!

The more detailed answer: Blocking or throttling and poor reputation that can take weeks or months to repair.

When you blast a large volume of email from a cold IP, inbox providers interpret that spike as a red flag. The most common outcomes are: Bulk folder placement (your email lands in spam instead of the inbox), throttling (the receiving server slows or defers your sends), or outright blocks (the mailbox provider completely prevents your mails from being delivered at all). In more severe cases, you can land on a blocklist that prevents your email from being delivered to any of that inbox providers’ users (and getting off a blocklist isn’t always fast or easy).

Real world example: A company migrates to a new Email Service Provider (ESP), skips warm-up because they’re under time pressure from leadership to show results, and pushes a promotional campaign to their full 500,000 subscriber list. Within hours, providers start deferring their messages. Their new IP is flagged, and the company spends the next six weeks doing damage control instead of maximizing revenue through their email campaigns.

It can be tempting to look for workarounds, but experienced email marketers have learned that’s a dead end. The math never favors skipping IP warming.

What a realistic warm-up schedule looks like

At Braze, we always recommend reviewing your organization’s expected sending volume, audience engagement, and long-term growth plans to build a bespoke strategy. That said, a typical warm-up schedule follows a doubling pattern over a 4-8 week span, depending on your ultimate maximum daily volume. Here’s a rough framework for a sender targeting ~1 million emails/month:

• Week 1: Start: 100-200 | End: 400-800 sends per day
• Week 2: Start: 800-1600 | End: 3,200-6,400 sends per day
• Week 3: Start: 6,400-12,800 | End: 25,600-51,000 sends per day
• Week 4: Start: 51,000-100,00 | End: 200,000-500,000 sends per day
• Weeks 5–8: Scale to full volume as reputation stabilizes

The key word is “consistent.” Sending 50,000 messages in one day and then nothing for a week is not a warm-up; it’s a reputation roller coaster. Inbox providers reward predictability, so try to send on a regular cadence even during the ramp. If your natural send volume is lower earlier on, keep the schedule modest and extend the timeline.

To make the warm-up process easier and more turnkey for marketers, the Braze platform now offers automated IP warming. Check out our documentation for more details on this feature and how to make the most of it.

Setting expectations with stakeholders

This is often the hardest part. Not the technical execution, but managing the internal pressure to send everything quickly. Marketing teams have campaigns queued. Leadership wants to see results. The temptation to rush is real.

Frame warm-up as a critical step in building a strong sending foundation for optimized performance rather than an obstacle to getting started. You wouldn’t launch a product on servers that haven’t been load tested. You wouldn’t open a restaurant the same day you signed the lease. IP warm-up is the same idea: It’s the setup that makes everything after it actually work. A 4-6 week ramp is a small investment compared to months of deliverability cleanup. That framing tends to land well with leaders who care about long-term ROI.

What “good” engagement looks like during warm-up

During warm-up, your deliverability metrics are live feedback that can help show whether you’re building reputation or burning it. Here’s what to watch:

• Spam complaint rate: Keep this below 0.10%. Above 0.08% and you should investigate. Above 0.30% is serious, and is likely to result in deliverability issues.
• Open rates: Especially early on, aim high. Starting with your most engaged subscribers and target 30%+.
• Bounce rates: Hard bounces above 2–3% suggest list hygiene issues that will compound deliverability problems.
• Inbox placement: Track your open rates over time. A sudden drop can give you an early indication of whether your mail is landing in the inbox versus the spam folder.

If metrics start trending in the wrong direction, slow down. It’s better to pause and reassess than to push through and dig a deeper hole.

Common pitfalls to avoid

• Warming on unengaged lists. Your warm-up audience should be your best subscribers, people who recently opted in and are very engaged and opened something in the last 90 days. Mailing to cold, stale lists during warm-up is asking for low engagement and/or complaints.
• Sending inconsistently. Big sending spikes followed by silence confuse inbox providers and can raise red flags. Aim for a steady, predictable cadence.
• Ignoring feedback loops. Sign up for feedback loop (FBL) programs with major ISPs. These tell you when recipients mark your email as spam, so you can suppress them before complaint rates climb. If you are a Braze customer, we automatically sign up for all available FBLs on your behalf.
• Assuming “delivered” means “inbox.” A message accepted by the receiving server doesn’t mean it hit the inbox. Open rates can be used as an indicator of inbox vs. spam placement. If open rates drop dramatically during warm up, particularly while “delivered” rates stay high, review the audience you are targeting to ensure it’s highly engaged and steadily building. If everything appears to follow the plan, you may need to slow down overall or specifically for the mailbox provider demonstrating issues.
• Skipping authentication. SPF, DKIM, and DMARC should be set up before you send a single warm-up email. These aren’t optional extras. They’re table stakes for good deliverability. If you are a Braze customer, we set up SPF and DKIM on your behalf before the first email is sent. You will need to set up DMARC on your own because it is a policy you publish in your own domain's DNS.

Tips for ESP migrations and new dedicated IPs

Migrating to a Braze or launching a dedicated IP are the two most common scenarios that require a warm-up. Both require the same preparation and discipline, but there are a few specifics worth calling out:

• Bring your suppression list. Don’t start fresh and re-mail people who already unsubscribed. Import your suppression list before sending anything.
• Don’t run re-engagement campaigns during warm-up. Save your risky, “we miss you” messages after your IP has built a strong reputation. Re-engagement campaigns mailed to inactive subscribers are magnets for complaints and low engagement, so tread carefully before sending.
• Split volume strategically during migration. If you’re moving from one ESP to another, consider running the two systems in parallel and gradually shifting volume to the new IP rather than cutting over all at once.
• General Tip: It is important to have one central place where all of your unsubscribes and complaints are stored and referenced. This is called a source of truth. Without it, your sending platform may not know who has opted out or complained, and could accidentally send to those subscribers. Mailing to unsubscribed or disengaged subscribers during your IP warm-up can hurt your deliverability and significantly slow down the process (plus, it may be restricted or prohibited under various laws).

The bottom line

IP warming isn’t bureaucratic red tape. It’s the mechanism by which you earn the right to reach people’s inboxes at scale. Done well, it’s largely invisible and your emails land where they’re supposed to, your metrics look healthy, and your stakeholders are happy. Done poorly or skipped entirely, it becomes the story of why your campaigns underperformed for an entire quarter.

Respect the ramp. Your future self will thank you. Email deliverability services here at Braze are a must when it comes to a smooth, professional IP Warming. And always remember: A good IP reputation is difficult to build but easy to destroy.

Interested in learning about IP warming and how to leverage it effectively to support your customer engagement goals? Check out our exclusive guide to IP warming.