Does Email Warm Up Work & Is It Necessary?

Are you wondering if you should use a warm-up tool before sending cold emails?

Many people in the cold email community advocate the use of email warm-up tools. However, in this article, I will explain why you shouldn't use them.

At best, they don’t do much to help, at worst, they could get your emails marked as spam by email service providers.

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 email warm up work?
- Are email warm up tools safe to use?
- 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 will happen by default.

The problem with some email warm-up tools is that 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 email 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 email warm up work?

The short answer is no.

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:

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 email 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. Email 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 warm up pools, since the type of email accounts found in warm up pools are not representative of the average email account that exists in the real world. For example, virtually all email accounts found in warm up 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.

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 email 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 email warm up tools safe to use?

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 email warm up tools. These are the most advanced companies in the world, and they can easily identify fake emails sent from email warm up tools. I recommend that you don’t use any email warm up tool, 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. Email 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:

Is email warm up necessary?

Email warm up is not necessary. I recommend that you don’t use an email warm up tool before sending cold emails because there is no evidence showing they work.

If you use an email warm up tool, the best case scenario is that it has no effect; the worst case scenario is all of your emails being marked as spam by email service providers.

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

The best way to avoid spam folders is to follow the advice in my article How To Send Cold Emails Without Landing In Spam.

I also recommend that you use Emailchaser to send your cold emails. Our email sending software is built for deliverability and will help your emails land in the primary inbox (not spam).

Email 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 (just like how email warm up is spam), and doesn’t work, isn’t long term sustainable, and is easily detectable by Google.

Now, I would never use PBNs as I know how to build quality backlinks from real authoritative websites. The same applies to cold email, I would never use an email warm up tool knowing what I know now.

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. Just because there are people willing to sell you email warming tools, doesn’t mean that they work, are safe or that you should use them.

Final thoughts

Email warm up tools that attempt to artificially manipulate your response rate by adding your email accounts to a warm-up pool are not effective.

These warming services are also unsafe as they are banned by email service providers such as Google and Microsoft. Email service providers will mark your emails as spam if you use warm up tools.

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 How To Send Cold Emails Without Landing In Spam.