Does Email Warm Up Work & Is It Necessary?

Correction, 9 August 2026. This article used to tell you that Emailchaser's Warm-Up Pool was the measurement kind, and that we had not built the fake-engagement kind I argue against below. That was not true, and it stayed up while it was not true.

Our warm-up pool simulates engagement. Mailboxes with warm-up switched on exchange email with other mailboxes in the pool, and that mail is marked as read most of the time, marked important most of the time, replied to some of the time, and moved out of the spam folder when it lands there. Those are manufactured signals. By the definition I use in this article, that is the thing I spent years telling people not to buy.

I have left the argument below exactly as it stood, because I still believe it. What has changed is that I now have to apply it to us. What our pool actually does is set out in full further down, including the parts that do not flatter us.

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Are you wondering if you should warm up your inboxes before sending cold emails?

Warm-up has become an expected feature on almost every cold email platform, so it's a fair question. But "warm-up" has quietly come to mean two very different things, and the difference is everything.

One kind is artificial warm-up: tools that add your account to a pool of other accounts that all email each other and fake replies, opens and "important" markers to manufacture a high response rate. This is the kind I've argued against for years — at best it does nothing, at worst it could get your emails marked as spam by email service providers.

The other kind is measurement-based warm-up: using real seed inboxes to actually measure where your emails land (inbox vs. spam) and ramping your sending volume gradually and safely. This one is legitimate, and it is the one I would defend.

I’ve been sending cold emails for many years, and have also built a leading cold email software (Emailchaser), so I am qualified to talk on this subject.

In this article, I will cover the following:

- What is email warm up?
- Does artificial email warm up work?
- Are artificial email warm up tools safe to use?
- What Emailchaser's warm-up pool actually does
- Is email warm up necessary?

What is email warm up?

Email warm up, also known as email warming, is the process of gradually increasing the number of emails that you send from a new email account.

The reason why some people think that email warm up is a good idea is because most email service providers will think that a sudden increase in email volume from a new email account is suspicious, causing your emails to go to the spam folder.

If you create a new email account, and you immediately send hundreds of emails, then your emails will go to spam.

The idea of email warming is to gradually increase the number of emails being sent from your new email account. If you send your cold emails with Emailchaser, then this gradual build-up is available on every plan.

So far, so sensible — a gradual ramp is a genuinely good idea. The problem is with what most warm-up tools bolt on top of the ramp. They don't just gradually build up your sending volume. They also try to artificially manipulate your response rate by adding your email account to a warm-up pool with other email accounts, and then all of these email accounts are used to respond to each other.

The idea is that this will improve your deliverability because email service providers will see that you have a high response rate.

The problem with this is that it's very obvious when an email account is part of an artificial warm-up pool.

Leading email service providers, such as Google and Microsoft, have advanced algorithms that can easily detect this. This means that right out of the gate, you've made it known to Google and Microsoft that you're trying to manipulate your response rate, and they will blacklist your email accounts.

Even the co-founder of Instantly (email warm-up software) admits at 15:07 in the below video that they used an external warm-up API to build their email warm-up feature. This implies that their warm-up feature is not advanced, and is something anyone could put together, meaning that Google and Microsoft will be able to detect these warm-up emails easily:

Does artificial email warm up work?

The short answer is no — not the artificial, fake-engagement kind.

Trying to artificially manipulate your response rate with email warm-up tools is not effective, and will cause your emails to go to spam as email service providers will blacklist your email accounts and domains.

Many companies offer email warm-up tools which add your email accounts to a warm-up pool. All promising “improved deliverability”, while providing zero evidence of any results.

At 05:31 in the below video, the founder of an email deliverability company called Folderly states that email warm up tools do NOT work:

The below video shows data on how popular email warm up tools decrease your reply rate (compared to using no warming):

There are many factors that affect email deliverability, and the idea that email warm up is the "silver bullet" of cold email deliverability is a myth perpetuated by companies that sell email warm up services. If you want to learn how to guarantee the best possible deliverability, then I recommend that you read my article 13 Ways To Prevent Your Cold Emails From Going To Spam.

Even if these warm up tools were effective, the question of whether they will remain effective long term is debatable since email service providers such as Gmail do not allow the use of them. Fake-engagement warm up tools are against Gmail’s terms of service.

Google has the world’s most advanced algorithms and AI. Do you really think they don’t know when email accounts in email warm up pools are sending fake emails to each other to manipulate response rates?

Companies that offer email warm up features often point to the number of email accounts in their warm up pool, as if this somehow means that Google and Microsoft can't detect the warm up pool due to the volume of accounts.

The reality is that it is still extremely easy for Google and Microsoft to detect emails from these warm up pools, since the type of email accounts found in them are not representative of the average email account that exists in the real world. For example, virtually all email accounts found in these pools will be brand new, and from either Google or Microsoft; it is not difficult to detect when an email account is part of a warm up pool when all of the emails being received are from email accounts that are not even remotely representative of the general population.

Fake-engagement email warm up tools are not effective, and the only people promoting them are financially incentivized to sell you them.

The below LinkedIn post shows how Erol Toker's email accounts were burnt (blacklisted) immediately when he used an email warm up tool:

The below Tweet shows that these warm up tools decrease your response rate:

Turn off warmup?

Tested lots with cold email over past 8 weeks

Our reply rates improved when not using warm up

Guys in my group have tested this too and seen similar results

Spoke to smarter guys than me who have also seen similar results

Might be worth testing

— Sean (@seanb2b) July 5, 2024

Are artificial email warm up tools safe to use?

Fake-engagement email warm up tools are not safe to use.

Email service providers such as Gmail don’t allow them and will blacklist your email address if you use them. It is against Google’s terms of service to use these tools.

The below tweet shows a statement from Google explicitly stating that email warm up tools are not allowed, and if used, will cause your emails to be marked as spam:

Whoa, just got this notice from Google.

Is this THE END of email warmup services?

Anybody else offering warmup get this? pic.twitter.com/TIMeMLfw3H

— Ajay Goel (@PartTimeSnob) November 16, 2022

Google goes even further, as shown in the below tweet:

Google is even more autocratic about the email warmup takedown than I expected. After informing them I've disabled the service, they sent me this.

I'm not even allowed to MENTION warmup of Google accounts anywhere on my site. pic.twitter.com/JUuyiVuLa0

— Ajay Goel (@PartTimeSnob) February 8, 2023

Even the founder of Gmass (popular email warm up tool) admits that email warm up is not safe and has shut down his entire warm up tool:

That's a wrap.

After sending 1,295,152,830 warm-up emails for 236,084 email accounts over two years, the GMass warm-up service is over.

All warm-up functions have ceased except the auto-archiver. I'll let that run for a few more hours.

So now what?

— Ajay Goel (@PartTimeSnob) February 1, 2023

To summarize, Google (Gmail) and other email service providers are clamping down hard on fake-engagement warm up tools. These are the most advanced companies in the world, and they can easily identify fake emails sent from email warm up pools. I recommend that you don’t use any warm up tool that manufactures fake engagement, as your emails will likely be marked as spam if you use them.

Additionally, it's possible that there are "spam traps" distributed inside of popular email warm-up pools, meaning that if you add your email accounts to those email warm-up pools, then your emails may be marked as spam. Think about it logically, if you were an email service provider trying to catch all of the people that are manipulating response rates, then adding spam traps to these warm-up pools would be an easy way of doing so.

Finally, one of the main factors affecting your deliverability is your total sending volume. Fake-engagement warm up tools contribute to your overall sending volume, which isn't a good thing. If you don't understand why your sending volume matters, then I recommend that you read my article How Many Cold Emails Can You Send Per Day Before Going To Spam?

The below video at 34:09 shows someone getting 86 email accounts blocked by Google when they used Smartlead's warm up tool for 2 weeks:

What Emailchaser's warm-up pool actually does

Everything above is about artificial warm-up: pools of accounts manufacturing engagement to move a reply rate. I called that detectable, ineffective and against the rules, and I still think all three.

We run one. Here is precisely what it does, taken from our own code rather than from a marketing page.

When you switch warm-up on for a mailbox, two things start. The first is the ramp: genuine sending volume, starting at around two emails a day and climbing to that mailbox's cap. That part is uncontroversial and it is what I have always recommended.

The second is the pool. Your mailbox exchanges email with other mailboxes that also have warm-up switched on. On the receiving side, our system signs into those mailboxes and:

- marks the message as read, roughly 70 to 100% of the time
- marks it important, roughly 70 to 100% of the time
- writes a reply to it, roughly 10 to 30% of the time
- moves it out of the spam folder and into the inbox, roughly 20 to 40% of the time when it lands in spam

There is no honest way to describe that as measurement. It is manufactured engagement.

What is genuinely different, and what is not

Three things about ours are different from the tools I criticise above, and I want to be careful not to oversell them.

- The mailboxes are real and already in use. A large part of my argument is that warm-up pools are easy to detect because they are full of brand-new, disposable accounts that only ever email each other. Ours are working business mailboxes that send real campaigns to real prospects and receive real mail. That makes the pattern harder to pick out. It does not make the signals genuine.
- It is off until you turn it on. Warm-up is switched on per mailbox, by you. Most platforms default it on, and for a period this year ours did too, by mistake, on mailboxes people had simply connected. That was a bug, we fixed it, and enrolment is now something you choose. Mailboxes you buy from us are the exception: nobody reads those, so they warm from the day they are set up.
- It never reaches your inbox as a lead. Every warm-up message carries a header our system recognises, so pool mail and its replies are dropped before they can become a lead, a reply notification or a row in your CRM.

What none of that changes: if Google or Microsoft decide a pattern of self-generated opens and replies is manipulation, being a real mailbox rather than a disposable one is a defence of degree, not of kind. The risks I set out above apply to us too. You should weigh them before switching it on, and the honest reason it is off by default is that I would rather you made that choice deliberately.

The measurement part is the part we have not finished

The version of warm-up I actually believe in is placement measurement: sending to real seed inboxes across the major providers and reporting whether your mail landed in the inbox, spam or a promotions tab. That is a number you can see and act on, rather than a reply rate you cannot verify.

We are building that, and it is not in the product yet. This article previously implied it was what the Warm-Up Pool already did. It is not. Do not buy Emailchaser for a placement report today, because there is not one to show you.

Is email warm up necessary?

The honest answer has not changed: no, and knowing where your emails actually land matters far more.

I do not think a manufactured reply rate helps you, whether it comes from a warm-up tool you buy separately or from ours. If you find the argument above persuasive, leave warm-up switched off. It is off unless you turn it on, and nothing else in Emailchaser stops working if you never touch it.

At 30:00 in the below video, Jesse Ouellette discusses how his company is now launching cold email campaigns without using (artificial) email warm-up tools:

That said, "don't fake it" is not the same as "fly blind". Two things genuinely help:

- Ramp gradually. Don't blast hundreds of emails from a brand-new mailbox on day one — build the volume up over time. This is the half of warm-up I have no reservations about.
- Measure your placement. Use real seed inboxes to see whether you're actually hitting the inbox, so you can catch and fix a deliverability problem before it burns your domain.

And the single biggest lever is still list quality. The best way to avoid spam folders is by only contacting people that actually need your product or service. You can learn how to do this in my article How To Create An Evergreen Cold Email Campaign.

The below video shows a conversation that discusses why artificial email warm up tools aren't effective:

Artificial warm up reminds me of Private Blog Networks (PBNs) in SEO. I’ve been doing SEO for nearly a decade, and when I first got started, a lot of people who were selling SEO courses were teaching the use of PBNs to build backlinks to websites. This method was spam, and doesn’t work, isn’t long term sustainable, and is easily detectable by Google.

I would not use PBNs today, because I know how to build real backlinks. I would say the same about manufactured engagement, and the uncomfortable part of writing this correction is that we ship it. The argument and the product are not aligned, and saying so publicly is the first step to fixing that rather than the end of it.

Even today, you can go to Fiverr and buy 5,000 spammy backlinks from someone. Just because the service is offered, doesn’t mean it is effective or safe. That test does not get an exemption when the company applying it is mine.

Final thoughts

Warm-up tools that manufacture a response rate by putting your accounts in a pool of accounts that engage with each other are, in my view, not effective, and they carry a real risk of being treated as manipulation by Google and Microsoft.

Emailchaser has a pool that does this. It is off unless you switch it on, it runs on working business mailboxes rather than disposable ones, and its mail never reaches your leads. Those differences are real, and they are still differences of degree. I would rather tell you that plainly than have you find it yourself and conclude we were hiding it.

The part I do believe in, measuring where your mail actually lands, is not shipped yet. Until it is, the things that genuinely protect your deliverability are unchanged: ramp gradually, authenticate your domain, keep your list clean, and only contact people who actually need what you sell (see How To Create An Evergreen Cold Email Campaign). If you want to see how we handle the rest of it, that is our cold email software.