What is Email Warmup?
Picture this: you just bought a brand new domain, set up a fresh email account, and you’re ready to send your first batch of 500 cold emails. You hit send on Monday morning, grab your coffee, and wait for the replies to roll in.
By Tuesday, you check your stats. Zero opens. Zero replies. You send a test email to yourself and find it sitting in your spam folder. Your brand new domain just got burned before you even got started.
This is exactly why email warmup exists.
Email warmup is the process of gradually building sending reputation for a new email account or domain. Think of it like breaking in a new pair of shoes. You don’t run a marathon in them on day one. You wear them around the house first, then for short walks, then longer ones, until they’re ready for the big race.
Email providers like Gmail, Outlook, and Yahoo are watching every sender. When a brand new account suddenly starts blasting out hundreds of emails, their spam filters light up like a Christmas tree. That account gets flagged, and everything it sends goes straight to spam.
Warmup solves this problem by establishing a pattern of legitimate, engaged email activity before you start your cold outreach campaigns.
Why You Absolutely Cannot Skip Warmup
Let me show you what happens in two different scenarios. Both start with the same goal: send 100 cold emails per day from a new domain.
In the first scenario, someone decides to skip warmup to “save time.” On day one, they send 100 cold emails. About 80% land in spam immediately. By day two, the domain reputation has tanked so badly that even test emails to themselves go to spam. By day three, the email provider starts throttling the account. After a month of struggling, they give up and have to start completely over with a new domain.
In the second scenario, someone does it right. They spend three weeks warming up the account gradually. In week four, they start sending cold emails at just 20-30 per day. By week five, they’ve scaled to 50 per day. By week six, they’re at their target of 100 per day with 95% inbox placement. Their emails get opened, they get replies, and they book meetings.
The math is brutally simple: three weeks of proper warmup saves you months of wasted effort, burned domains, and lost opportunities.
The Complete Warmup Timeline
Let’s walk through exactly what you need to do, week by week, to properly warm up an email account.
Phase 1: Initial Setup (Day 0)
Before you send a single warmup email, you need to make sure your foundation is solid. Your domain should be at least two weeks old, ideally four weeks or more. Fresh domains registered yesterday scream “spam” to email providers.
You also need to configure your technical authentication properly. That means setting up SPF, DKIM, and DMARC records. These are the security protocols that prove you actually own the domain you’re sending from. Without them, you’re done before you start.
One critical point: never use your primary business domain for cold email. If you burn your main domain, you’ve just killed your company’s ability to send any emails at all. Use a secondary domain that’s similar to your main one, like “getflowleads.com” instead of “flowleads.com.”
Set up a professional email address with a real person’s name, add a profile picture, and create a basic email signature. These small details signal to email providers that this is a real human, not a spam bot.
Phase 2: Early Warmup (Days 1-7)
This is where the actual warmup begins. You’ll start with just 5-10 emails per day. I know this feels painfully slow when you’re excited to start reaching out to prospects, but this patience pays massive dividends.
Here’s what’s happening behind the scenes when you connect to a warmup tool. The tool sends emails from your account to other accounts in its network of thousands of users who are also warming up their emails. Those accounts automatically open your emails, reply to some of them, and mark them as “not spam” if they happen to land in the spam folder.
At the same time, your account receives warmup emails from other people in the network, and the tool makes your account open them, reply to some, and move them from spam to inbox. To email providers watching this activity, it looks like you’re a normal person having normal email conversations with people who actually want to hear from you.
During this first week, you need to monitor things closely. Check every day to make sure your warmup emails are landing in your inbox, not spam. Look for consistent open and reply rates in your warmup tool’s dashboard. If you see any bounces, errors, or warning messages, stop and fix them before continuing.
The red flags to watch for: warmup emails going to spam means your authentication setup is wrong. High bounce rates mean your email configuration has problems. If your account gets suspended, you’ll need to contact your email provider to sort it out.
Phase 3: Building Volume (Days 8-14)
In week two, your daily volume increases to 20-30 emails. This happens automatically if you’re using a warmup tool. The engagement patterns from week one continue, but now they’re happening at higher volume.
This is when your sending reputation really starts to form. Email providers have now seen consistent activity from your account for over a week. They’re starting to trust that you’re legitimate.
If you’re using Google Workspace, you can check Google Postmaster Tools to see how your domain reputation is trending. Monitor your warmup tool’s dashboard daily to make sure engagement rates stay high. If you see any warnings from your email provider, address them immediately.
You can also start sending a few real emails during this phase. Send messages to colleagues, friends, or business contacts you know well. Ask them to reply to help build your reputation. These authentic conversations mixed with automated warmup create the most natural-looking pattern.
Phase 4: Pre-Launch (Days 15-21)
You’re now sending 40-50 warmup emails per day, and your reputation is established. You’re almost ready to start real cold outreach, but not quite yet.
This third week is your final validation period. Run a deliverability test using a tool like Mail Tester or GlockApps. These services show you exactly how different email providers will treat your messages. You want to see a score of at least 9 out of 10.
Double-check that all your authentication is passing. Verify your domain reputation status. Prepare your first cold email campaign, but don’t send it yet.
Before you launch, you need to pass these criteria: Mail Tester score of 9 or higher, inbox placement rate of 95% or better, no emails landing in spam, and no blacklist warnings. If you don’t hit all of these marks, keep warming up for another week.
Phase 5: Launch and Scale (Day 22+)
This is the moment you’ve been waiting for. You can finally start sending real cold emails. But here’s the critical part that most people get wrong: you don’t stop warming up.
Your best approach is to continue warmup at 20-30 emails per day while adding real cold outreach at 20-30 emails per day. Your total daily volume is now 40-60 emails, split between warmup and outreach.
Then you scale gradually. In week four, send 20-30 cold emails per day. Week five, increase to 30-40 per day. Week six, go to 40-50 per day. By week seven and beyond, you can safely send 50-100 cold emails per day.
Never exceed 100 emails per mailbox per day. If you need more volume than that, don’t increase the number from a single mailbox. Instead, add more mailboxes and warm each one up properly.
How Warmup Tools Actually Work
When you connect your email account to a warmup tool, you’re joining a network of thousands of other users who are all warming up their accounts too. Your account sends emails to random accounts in this network, and those accounts automatically engage with your messages.
The warmup tool makes those receiving accounts open your emails, reply to a percentage of them (usually 30-50%), and move your messages from spam to inbox if needed. They also mark your emails as “not spam” when prompted by their email provider.
At the same time, your account receives warmup emails from other users in the network. The tool automates your account to open those messages, reply to some, and take the same positive engagement actions.
Why does this work? Because email providers track specific engagement signals to determine if you’re a legitimate sender. Opens tell them “this sender is wanted.” Replies tell them “this is a real conversation between real people.” “Not spam” actions tell them “users have confirmed this isn’t spam.”
Warmup tools manufacture these positive signals at scale, building your reputation without requiring you to manually send hundreds of emails to your personal contacts.
Best Email Warmup Tools for 2025
You have two main options: tools that combine warmup with cold email sending, or standalone warmup tools you can use with any sending platform.
For built-in warmup combined with sending, Instantly is the best choice at $37 per month. You get excellent warmup capabilities plus a full cold email sending platform. Lemlist and Smartlead also offer good warmup with sending, though at slightly higher price points.
If you need standalone warmup because your sending tool doesn’t include it, Lemwarm is the most reliable option at $29 per month with a network of over 20,000 users. Warmbox is a solid budget alternative at just $15 per month with an even larger network of 35,000+ users.
When you set up a warmup tool, start with conservative limits and enable the feature that automatically moves emails from spam to inbox. Configure the reply rate to something natural, like 30-50%, and set warmup emails to send only during business hours. Monitor the dashboard closely for the first few days to catch any issues early.
What If You Can’t Use Warmup Tools?
Maybe you’re in a situation where you can’t access warmup tools due to company policy, budget constraints, or technical limitations. Manual warmup is possible, it’s just more time-intensive.
In the first week, send 5-10 emails per day to friends, family, and colleagues. Ask them explicitly to open your email, reply with anything, and mark it as “not spam” if it lands in their spam folder.
In the second week, expand to 15-20 emails per day sent to your extended network. Reach out to LinkedIn connections (after asking for their email first), newsletter subscribers, or past customers. Continue encouraging them to open and reply.
In the third week, you need to get creative. Send 30-40 emails per day by creating secondary accounts to email yourself, joining email warmup communities where people exchange emails to help each other, or finding other cold email senders to partner with.
The downsides of manual warmup are significant. It’s incredibly time-intensive, much less consistent than automated tools, and nearly impossible to scale if you need to warm up multiple mailboxes. Use tools whenever possible. Manual warmup is truly a last resort.
Different Scenarios Need Different Approaches
A brand new domain with a brand new account is the highest-risk scenario. You have zero history and zero reputation. For this situation, wait at least two weeks after purchasing the domain before even starting warmup. Then run warmup for a full three weeks. When you start cold outreach, be extremely conservative with just 10-20 emails per day for the first week. Scale slowly over the next four to six weeks.
If you’re adding a new account to an existing domain that already sends email, your timeline is shorter. The domain already has some reputation, so you only need two weeks of warmup. Then you can start cold outreach at 20-30 per day and scale normally.
Reviving an inactive account that hasn’t sent email in three or more months requires one to two weeks of warmup. First, send some test emails to check current deliverability. If it’s good, one week of warmup is enough. If deliverability is poor, run two weeks of warmup and start slowly.
If you’re trying to recover a burned domain that was blacklisted or has terrible reputation, you face a difficult choice. You can wait it out by stopping all cold email and running warmup-only for six to eight weeks. You can start fresh with a new domain and proper warmup. Or you can use a hybrid approach with a new domain for cold email while repairing the old one for warm outreach. Honestly, starting fresh is usually faster than trying to recover a burned domain.
The Biggest Warmup Mistakes to Avoid
The most common mistake is warming up too fast. Increasing volume by more than 20% per day triggers alarm bells with email providers who see sudden changes as suspicious. Keep your volume increases gradual and consistent.
Another critical mistake is stopping warmup completely once you start cold outreach. When warmup stops, your engagement signals drop and your reputation starts to decline. Keep warmup running continuously at about 20-30% of your total sending volume.
Some people try to save money with cheap warmup tools that have low-quality networks. The problem is that these networks often include spammy accounts, and being associated with bad actors hurts your reputation. Use reputable tools with quality networks.
Ignoring warmup metrics is dangerous. If you’re not monitoring performance, you’ll miss early warning signs of problems. Check your warmup dashboard daily for at least the first two weeks.
Finally, some warmup tools use obviously automated, generic content that sophisticated email providers can detect and discount. Choose tools that use varied, natural-looking email content that simulates real human conversations.
Maintaining Long-Term Email Health
Warmup isn’t something you do once and forget about. It’s ongoing maintenance that protects your sending reputation.
Even after you’ve scaled to full volume, keep warmup running at 20-30 emails per day. This maintains your engagement signals and protects against reputation decay over time.
Stick to the golden rule: never exceed 100 cold emails per mailbox per day. If you need more volume, add more mailboxes and warm each one up properly.
All the warmup in the world won’t help if you’re sending to invalid addresses. Verify emails before sending, remove bounces immediately, and clean your lists at least monthly.
Finally, maintain human-like sending patterns. Send only during business hours, vary your send times slightly each day, take weekends off or at least significantly reduce volume, and avoid sending everything in one massive batch.
Key Takeaways
Email warmup is absolutely non-negotiable for cold outreach success. The minimum warmup period before any cold outreach is two to three weeks. Start with just 5-10 emails per day and increase by 5-10 emails daily. Use automated warmup tools to simulate real engagement at scale without requiring manual effort.
Continue warmup in the background even after you’ve scaled to full volume. This ongoing warmup maintains your reputation. Remember that new domains need warmup, and even existing domains need it after periods of inactivity.
If you skip warmup, you’re throwing money away on emails that never get seen. The time invested in proper warmup pays back exponentially in deliverability, response rates, and ultimately, closed deals.
Need Help With Email Infrastructure?
We’ve built and managed email systems that handle millions of cold emails per month with 95%+ deliverability rates. We know every pitfall, every edge case, and every optimization that makes the difference between spam and inbox.
If you want your warmup and infrastructure set up correctly from day one without learning through expensive mistakes, book a call with our team. We’ll show you exactly how we’d set up your cold email system for maximum deliverability and results.