New to email outreach? Here's the rule: you can't start sending hundreds of emails from a fresh inbox.

You warm up first.

Email warmup builds your sender reputation with inbox providers like Gmail and Outlook, so fewer of your emails end up in spam.

A solid warmup is the difference between getting replies and getting filtered out.

First, the basics: what is email warmup?

It's the process of gradually increasing how many emails you send and how often you send them.

An inbox is "warmed up" once it has a steady history of sending and receiving messages.

Volume alone isn't enough. Your warmup emails need real engagement: replies, opens, clicks. Engagement tells inbox providers your emails are wanted, not noise.

So how long does warmup take? Around 3 to 4 weeks of warmup activity, plus 2 more weeks of stabilization at full volume before your inbox is ready for real campaigns.

Before that, you need a strategy. Most people get stuck on the same questions:

You can warm up manually or use a tool. We'll cover both.

💡Before starting, make sure you understand the difference between email and domain warmup and what lemwarm actually warms up.

Hours spent writing a great cold email mean nothing if it lands in spam.

Warmup builds your sender reputation, and reputation is what gets you into the inbox. Spam filters give trusted senders the benefit of the doubt. Your bounces drop. Your spam placement drops. Your open rates go up.

The result: more replies, more meetings, more revenue. Warmup is the foundation everything else sits on. For a deeper look at why this matters, the deliverability masterclass and deliverability eBook are good starting points.

For most senders, yes.

Two reasons:

If you're sending a handful of emails a week, manual warmup works. If you're running real outreach, you need a tool.

Want to try it manually anyway? Here's how to warm up an email by hand:

Warmup isn't a phase. It's ongoing.

Outreach naturally has lower engagement than personal email, so without warmup running in the background, your reputation slowly drops. Warmup keeps the engagement signals consistent.

Stop warmup, and your deliverability goes with it.

That's the main reason manual warmup falls apart: it's not a project, it's a habit. You'd spend hours a day on it, every day. A tool makes that automatic.

A warmup tool sends and receives warmup emails through your inbox automatically. You set it once, it runs in the background.

The tool sends from your account, replies arrive in your inbox, and the conversations look like real ones.

lemwarm is the best email warmup tool we know of, and it's not close. Customers regularly hit 80%+ open rates with it running. The full lemwarm review covers the features in depth.

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Total warmup time is around one month: 3 to 4 weeks to reach max volume, plus 2 weeks of stabilization at the top before you launch real campaigns.

Recommended lemwarm settings (current guidance, no matter your inbox age):

The ramp builds naturally. No spikes.

Once warmup is done, leave it on. That's how you keep deliverability where it should be.

💡 The right time to start campaigns is when your lemwarm score is over 90 AND you've been at 40 emails per day for 1 to 2 weeks. Time and score, both. Don't launch on time alone. Full setup details are in the help center: How to set up and use lemwarm.

lemwarm sends real emails from your inbox to other lemwarm users. The network spans 20,000+ healthy domains across 100+ countries.

No fake addresses. Real inboxes, real engagement.

The warmup emails use real-life templates that look like normal business correspondence. Replies come back on the same thread, threaded the way a human reply would be. To inbox providers, this looks like everyday email, because it is.

On the Smart plan, you can also warm up your real email templates. You add up to 5 templates with the exact subject lines and body copy you plan to send, and lemwarm warms them inside the network for 3 to 7 days before you launch. Each template gets its own spam rate, and lemwarm pauses any template that starts trending the wrong way.

Setup takes a few minutes. Once you sign up, the dashboard walks you through it. The full step-by-step is in the help center: lemwarm setup guide.

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Two options on the pricing page, both billed per email per month.

Yearly billing saves 20%. Quarterly saves 10%. lemwarm is also free with any active lemlist subscription. For the full feature comparison, see Discovering lemwarm Plans.

Open Settings, then Sending settings, then click Connect email address.

Pick your provider on the next screen. Google and Microsoft connect with one click. For other providers, you'll add SMTP and IMAP details. Full instructions: Connect an email address to lemwarm.

Click "Verify your email address." A confirmation link goes to the inbox you signed up with. Click it, and you're ready to warm up.

Verification also unlocks the technical setup check, which tells you if anything in your DNS is off. Your technical setup directly affects deliverability and includes:

From the dashboard, click Start lemwarm, then click Confirm. Warmup emails begin sending immediately.

💡 Set up a filter in your email provider so lemwarm emails skip your primary inbox. Replies pile up fast and you don't want them mixed in with your real mail.

Every domain is different. lemwarm lets you adjust settings based on your domain age and business so you get the most out of warmup.

Open the Warm up tab from the left sidebar to manage settings.

Set your daily limit to 40 emails per day from the start. That's the target capacity, and it should match the volume you plan to send with lemlist later.

The ramp-up still happens gradually under that ceiling. Most inboxes reach 40/day within 3 to 4 weeks. Then hold there for 2 more weeks before you switch over to real campaigns.

While lemwarm is ramping, keep lemlist at 1 email per day. No spikes, no shortcuts. If you do adjust sending, change it by small percentages each day (5% or 10%), not big jumps.

For tailored warmup emails, the Smart plan adjusts the warmup network to match your industry and audience.

Inbox providers read your email content and judge whether it matches your business. Generic warmup looks suspicious. Industry-relevant warmup looks legit.

This personalization is one of the simplest ways to get more out of warmup. Set it up and forget it.

The lemwarm score shows you how your inbox is performing. Three ranges: red, orange, green.

Red: don't start campaigns. Usually means a DNS or configuration issue, or risk of blacklisting. The dashboard tells you what to fix.

Orange: warming up. You can send, but keep volume low.

Green: you're ready. Launch campaigns and keep lemwarm on to hold the score.

How the score breaks down:

If your inbox rate is 98 to 99% over the last 2 weeks, your score lands around 91 to 93. If your score sits between 80 and 90 even after reaching 40/day, your domain probably has an issue raising spam rate. Stay at the same volume longer and dig into your setup.

Below the score, you'll see your inbox vs. spam ratio, total warmup emails sent, the Cold Email Performance graph (inbox in green, spam in red), and the Reply Performance graph. Use them to spot trends before they cost you replies.

At 40/day for 2 full weeks, expect:

Initial warmup takes about 4 weeks plus 2 weeks of stabilization. After that, three things to keep doing:

Warmup never ends, because reputation never stops being evaluated.

Email warmup may seem like a complicated concept at times. To simplify it, keep these three things in mind:

A plan to build sender reputation for new domains or domains with a poor track record. Newer domains need a slower ramp. Older domains can move faster. More on the basics here.

2 to 5 per day for the first 5 days. Increase incrementally after that. With lemwarm, you set the daily limit to 40 from day one and let the ramp build under that ceiling.

Yes. The good ones move the needle on deliverability. Some of the cheap or sketchy ones cause damage, so pick carefully.

lemwarm. Real inboxes, content tailored to your business, and alerts when something breaks. Sign up here.