Email Warm Up

Why email warm up is so important for deliverability?

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Email Warm Up | Breakcold
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A short explanation

What is email warm up?

When you want to start cold emailing, your first move is to create a sending address to carry on your cold email outreach. Most of the times, you start from a new address that needs to be 'warm up'. The process of warming up a domain means that before doing cold emails, you need to send emails to other email addresses with high domain reputation little by little before sending between 60 to 80 cold emails a day (we recommend to not go beyond per day). ‍‍‍ You can either warm up your email manually or with service providers.

Right domain | Email Warm Up
Buy a professional domain
You don't want to send cold emails with a regular email address such as You need a professional email address before warming it up.
Right extension | Email Warm Up
Choose a right extension
Domain extension is important. Google and Outlook represent more than 90% of email recipients. They value extensions with '.com' or '.co'.
Domain contamination | Email Warm Up
1 email address per domain
If you send 200 emails per day with 3 sending addresses from the same domain or from different accounts under the same domain, it's like sending 600 emails per day which is bad.

Email engagement is the #1 metric for email warm up

As stated above, Google and Outlook represent more than 90% of email recipients. In numerous documentations and statements, they told the public that engagement was the principal metric for deliverability.

It's simple, if you send 200 emails per day and that your reply rate is only 10%, by default your deliverability will decreases overtime.

This is why you need to warm up your email domain not only at the beginning of its cold email life but also during all its lifetime. This is the only way you can ensure not falling into spam even by not sending lots of cold emails per day.

Playbook | Email Warm Up

Set up SPF, DKIM and DMARC to increase deliverability

Sender Policy Framework (SPF), DomainKeys Identified Mail (DKIM) and Domain-based Message Authentication (DMARC) are email settings that you can make to ensure to increase your deliverability. Basically these settings when they are done prevent someone else from sending emails on behalf of you by using your domain address. SPF, DKIM and DMARC can be set in your domain hosting provider. Just write SPF, DKIM and DMARC with the word documentation and you will find it. You can also find a big list for each providers on Mailtester.

Settings | Email Warm Up

The importance of Custom Tracking Domain for email warm up

When you send emails from a cold email software or even from an email marketing software, they mostly use a tracking url code. This invisible code allows the software to display you the open rate for example and many other metrics that you can use to improve your skills at cold mailing. However, you share this code with other users. Simply put, it means that if some users of the software are spammers, you will suffer a tiny bit from their behavior because you share the same invisible tracking code as them. By enabling what is called Custom Tracking Domain, you will be able to avoid these kind of problems. The tracking code will be directly linked to your domain and not shared with other people.

Custom Tracking Domain | Email Warm Up
Email warm up Q&A

Common asked questions on email warm up.

How long does it takes to warm up an email address?

It can takes anywhere from 14 days up to 21 days to warm up an email address. If you do it manually, it can take even longer. We recommend to send emails little by little every day and finishing around a strong 30/40 emails per day.

How many cold emails per day should I send?

While you are warming up your email address, you must not send any cold emails. Once your email is warmed up, you should send around 50 to 70 cold emails max per day. Some people send 200 cold emails per day but this is a dangerous maximum to go without affecting your deliverability.

Is there any words I should avoid to fall in spam?

Some words are considered as spam by Google or Outlook and other providers. Anything that sounds pushy, insults and contain promotional words are considered as spam words.

How can I run a spam test?

You can run a spam test on Mailtester but beware of the results of this test because you can have a score of 10/10 but still going into spam in both short-term and long-term. You might have a perfect score on Google but going into spams on Outlook. Best spam checks are done with different email addresses from different service providers.

What is domain contamination and how to avoid it?

Let's say you send cold emails from 3 different sending email addresses under 1 Gsuite account. 2 addresses are warmed up and 1 is not. If you send 100 cold emails per day with the one that is not warmed up and that it got banned for being a spam, your other 2 email addresses will be contaminated and also be considered as spam.

How to warm up an email address manually?

Simply send to email addresses you either possess or you know and fake interactions for a few weeks. You need to diversify the type of email address as much as possible.

What is a good email format to avoid spams?

Before warming up an email address, choose something that sounds human and not generic such as Rather go with a human like email such as

Can I send images, links and videos when I do cold emails?

In theory you can but try as much as possible to avoid links, images, HTML format of some sort when doing cold emails. All these details can affect your deliverability and slow down your email warm up process. Be careful about your email signature, you need to get rid of the links that point towards your website and even of your company image.

Email warm up feature with Breakcold soon?

The plan for Breakcold is to offer a simple solution for its users. This is why we want people to be able to handle the whole email process from warm up to sending emails.

At the moment, the email warm up feature is not yet available but you can follow its evolution on our public roadmap.

Ready to test the future of cold email outreach?