Email Warmup Made Easy for Cold Email Success

You’ve got your lead list, verified it, ensured your copy is perfect, and everything is in order, but your cold email still gets no replies. This is probably because it ended up in the spam folder. Now, there is no way for you to know, but there are a few reasons this could happen. One of the biggest ones is the lack of email warmup. You see, most deliverability issues don’t come from what you write; instead, they come from how you send it.

In this piece, we will get into the nitty-gritty of what is email warmup, how to master it, the common mistakes that people make, and how teams improve their performance through smart, automated warmup systems.

What is Email Warmup?

In order to understand how email warmup works, let’s look at a simple analogy: It is your first day at the gym, and you do 100 deadlifts. What is the result? Muscle pain and a potential medical bill are waiting for you. When you go to the gym, you start by building up your body by doing easy tasks so you can one day do 100 deadlifts.

Email warmup works on the same principle. It is the process of gradually sending emails from a new email address to build sender reputation and increase deliverability. Many experts would also say that it is the first step in launching your cold email campaign. Email warmup teaches inbox providers that you’re a safe, trusted sender over time.

The warmup phase involves your email address slowly increasing sender volume, receiving replies, and interacting with other warmup accounts in a natural, human way. In other words, this simulates actual human behaviour and helps you avoid spam filters. A high-quality email warmup service or tool handles this automatically, often using a network of active, aged inboxes to create positive signals like replies and opens. It doesn’t matter if you’re using manual methods or advanced email warmup tools; the goal remains the same: build enough trust with Gmail and Outlook so your emails land in the inbox.

Why Email Warmup Matters for Cold Emailers

Email warmup for cold emailers is not an option; it is something that needs to be done. This is because major ESPs like Google and Outlook use some signals to decide if your emails end up in the inbox or the junk folder. Some of these signals include your authentication setup and your domain reputation.

So if you’re thinking of skipping email warmup, you’re sending from a cold domain or inbox with no history or trust. That is exactly what spam filters look for. Take a look at why email warmup tools are a must-have for cold emailers:

• Help build a positive domain reputation from Day 1
• Improve inbox placement  (landing in primary inbox)
• Avoid the spam folder
• Simulate real engagement (opens, replies, marking emails as not spam)
• Automate daily sending to mimic natural behaviour

It doesn't matter if you are starting out or running campaigns already; email warming up is a consistent and constant process.

Common Email Warmup Mistakes (And How to Avoid Them)

There are things you should definitely not ignore while setting up your email warmup, and then there are things that you should avoid at all costs…because if you don’t, then it is going to cost you.

1. Volume Ramped Too Fast

Many inexperienced cold emailers think the more, the better, but that is definitely not the case for new cold emailers. Senders make the error of starting their campaigns with 50–100 emails per day right out of the gate. This is nothing but a huge red flag. Mailbox providers are extremely sensitive to sudden spikes in sending volume, especially when they come from a new domain.

2. Poor Quality Warmup Pool

If the pool you’re using is made up entirely of secondary domains, other cold emailers, or newly created inboxes, your warmup efforts might be doing more harm than good. If you want your email warmup service to work well, it needs to have access to aged accounts, real inboxes, and a healthy mix of email service providers (ESPs). That’s because you’re not just trying to show that you can send emails, you’re trying to prove to inbox providers that your emails are valuable and trusted by a diverse network of recipients.

3. No SPF, DKIM, or DMARC

You could use the best email warmup tool in the world, and that still won’t mean anything if you didn’t authenticate your email. If you did not set up your SPF, DKIM, and DMARC properly, email providers have no way to verify that your messages are legitimate. That usually results in one of two outcomes: your emails get rejected outright or dumped straight into spam.

4. Very Low Reply Rates

Most people think that email warmup is about just sending. They’re wrong, though. It is just as much about receiving. If you’re sending countless emails a day and not getting any replies during the warm-up period, your domain reputation will suffer. Inbox providers pay close attention to engagement when deciding where to place your emails. Warmup activities that don't include positive interactions (like opens and replies) will ultimately hurt your deliverability. As a result, high-quality email warmup services simulate real replies and engagement patterns and help you build a reputation with both the algorithm and the human at the other end of the inbox.

5. Warming Up with Blacklisted Accounts

This one’s a silent killer. You never want to send or receive emails from inboxes that are already flagged or blacklisted. This is because your emails get associated with that negative history. Over time, your own sending reputation takes a hit even if your technical setup is fine. Senders don’t even realise this is happening until their reply rates drop or inbox placement tanks. A trustworthy email warmup service will constantly monitor the health of its pool and pull out any compromised accounts.

How Email Warmup Works: A Step-by-Step Breakdown

Now that you know what email warmup is and why it matters, let’s take a closer look at how it works. There are two options on how you could warm up your domain. You could do it manually, which is typically a lot of work, or you could automate the whole process by using an email warmup service of your choice.

Step 1: Start Slow and Steady

The first rule of email warmup is to begin with a small number of emails per day. Here's a warmup schedule recommended by experts.

The goal is to reach around 30–35 emails/day with a reply rate of at least 40–45% by the end of the warmup cycle.

Step 2: Simulate Human Behaviour

Looking suspicious is the last thing you want to do during email warmup. In fact, you’re doing quite the opposite. The best email warmup services simulate real inbox activity. That includes:

• Consistent sending: Emails are sent daily to mimic natural usage
• Random timing: Messages go out at varied times, not in predictable batches
• Engagement: Warmup accounts open, read, and reply to emails
• Spam correction: If emails land in spam, they're marked “Not Spam” to teach inbox filters

Step 3: Warmup Do’s and Don’ts

A smart, consistent email warmup strategy is what separates teams that get replies from those that get spam-filtered.

Choosing the Best Email Warmup Service

Choosing the best email warmup service for your business or product is a no-brainer, but understand that email warmup tools vary in quality. In fact, most cheap email warmup services rely on networks filled with cold outreach accounts or secondary domains. Basically, other cold emailers.

1. Balanced Warmup Pool (Cold + Non-Cold Accounts)

A good email warmup tool would not rely only on cold outreach accounts. Warming up with just secondary domains or other cold emailers is ineffective. So, look for a service that uses a healthy mix of cold and non-cold inboxes. Aged accounts that have a real sender history will give better results. We use Warmupinbox.com for our clients (It’s free!).

2. Domain Age & Sender Reputation

Older accounts mean older domains. Domain reputation improves faster when warmup emails are sent to trusted, aged inboxes.

3. ESP (Email Service Provider) Diversity

We know that Gmail is the most popular option out there, but it is not the only one. You see, Gmail-only pools don’t reflect real-world sending. Moreover, there is another contender, and it’s called Outlook. The best email warmup services include a mix of both. This helps simulate varied environments, which improves reputation across platforms. However, your best bet would be Aerosend because we’re an inbox infrastructure made for cold emailing, so you know your emails won’t go to spam.

4. Low Bounce Rates from the Warmup Pool

If there is one thing that could hurt your warmup pool the most, it is high bounce rates. Make sure your email warmup service has strict checks to avoid invalid emails. You can ask for a bounce rate report from the service you use. Any quality tool would be able to provide them.

5. Built-In Defence Systems

Your warmup provider should rescue and mark emails as NOT spam if they land there. Why is this necessary? Because Spam flag reversal and auto-engagement (replies, stars, archives) boost trust. You don’t just want delivery, you want to simulate real human behaviour.

6. Engagement Simulation

Let’s say you sent 10 warmup emails every day. If all of them get opened and replied to, also at the same time, that pattern is immediately suspicious to ESPs. These metrics can be positive, but only when used smartly. Make sure to read how your warmup tool of choice handles these metrics.