Get 20% OFF for your first month with the Starter Plan – Start today 🎉
Table of contents

Email Warm Up : All You (Really) Need To Know in 2023

damien ceo mailreach
Damien Brenelière
Co-Founder @ MailReach & Email Deliverability Expert

Email warm up is a practice increasingly popular to improve the results of email campaigns. In this article, we'll cover what is email warm up, why it's a game-changer to land in inbox, how to do it the best way and how long it takes. Let's dive in.

Email warm up : the way to make your company take off like a rocket

What is email warm up?

Email warm up is the process of preparing an email address, domain and IP to build a positive sender reputation with inbox providers and, as a result, land more often in the inbox of your recipients.

The goal of email warm up is to maximize the results of your campaigns with an optimized deliverability that will lead to higher open rates and, in turn, improve the reply, lead, click rates.

At the end of the day it helps you make more sales.

Years ago, email warm up only consisted in gradually increasing the volume of emails sent until reaching your daily volume goal. It was enough at that time as email deliverability was a lot easier.  

Today, in order to be really effective, email warm up has to be done by gradually increasing the volume of emails AND having a high engagement rate on your email activity to show the inbox providers that you’re a legit, interesting sender who deserves to land in inbox and not in spam.

In practical terms, email warm up consists in sending emails, having most of them opened, replied, marked as important and removed from spam if needed.

There are two ways of warming up your email account, automatically or manually. We'll cover that further in the article.

Why email warm up is crucial to reach the inbox of your recipients.

1. Email warm up helps you build, maintain and repair your sender reputation.

In 2023, the engagement rate on your emails is a top factor used by inbox providers such as Google and Microsoft to score your sender reputation which directly impacts your ability to land in inbox.

Here are quotes of leading companies in the email field about that:

ReturnPath: "Gmail uses engagement as a factor for filtering your email."

SendGrid: “The higher your email engagement, the more likely you are to avoid spam filters and land in the inbox.”

CampaignMonitor: “Now, whenever you send a new campaign, inbox providers like Gmail and Outlook actually look at their user engagement and previous interactions with your past campaigns. They then use this information to determine whether your latest campaign makes it to the inbox or not.”

And that makes a lot of sense that Google and Microsoft operate this way. Analyzing the engagement received on your emails is the best way for them to see if you're a good, interesting sender or if you're a nasty spammer.

As we said above, email warm-up is the act of sending emails, having most of them opened, replied positively, marked as important and removed from spam if you landed there.

In other words, email warm-up generates a perfect sending activity with maximum engagement. This definitely helps you build and maintain a positive sender reputation.

In addition to help you build a good sender reputation, email warm up also helps restoring a damaged one.

MailReach email warm up repairing a damaged sender reputation
Here's a graph of an email sender reputation getting repaired by MailReach's email warm up tool.

We go further into this in our famous helpdesk article : How to restore a damaged email reputation and deliverability using MailReach.

A bad sender reputation is the result of having too few positive interactions and too many negative ones (spam complaints). A bad sender reputation directly leads to landing in spam.

The best way to restore a damaged email reputation is to receive as many positive interactions (engagement) as you can to show the providers that you changed your practices, get much more engagement and, as a result, you're now a good sender.

MailReach's warm up service is a great help on that and we manage to restore a damaged reputation in 90% of the cases.

2. Email warm up improves deliverability and open rates when sending cold emails

Keep in mind this formula : deliverability = sender reputation (inbox, domain, IP) + sending setup + email content.

To achieve a perfect deliverability, you need :

  • A great sender reputation (on the inbox, domain and IP level).
  • To send non spammy emails: a clean email content without any spammy element.
  • From a non spammy sending setup: a way of sending that is well known and that is liked by Google and Microsoft.

As said earlier, warming up your mailbox helps you build, maintain and restore a great sender reputation. As a result, it raises your deliverability by improving your reputation.

About sending non spammy emails, checking if your content passes the spam filters, you can do that without hassle by using our free Email Spam Test.

That's the same process to check if your sending setup is not spammy: our free Email Spam Test will help you find out the impact of it.

3. Email warm up is the best way to monitor your sender reputation

One of the many benefits of email warmup is to help you follow and measure your sender reputation and deliverability. That’s very useful to know where you stand.

A screenshot of MailReach's email warm up service

The above graph is what you see on your MailReach dashboard when doing your email warm-up. This graph shows you the inbox placement of your warm up emails.

As it’s important to keep warming while you send your campaigns, this graph is a huge help since it helps you know how your sender reputation is doing.

If you land more and more in spam when sending, it means there’s something wrong with your campaign. It can be that you send too many emails, or you receive too many spam complaints, etc.

4. Sending cold emails without email warm up will lead to spam sooner or later

By default, when sending cold emails, your sender reputation is doomed to decrease week after week, month after month.

Why? Because you're reaching out to people you never contacted before and you are exposed to having a low engagement rate and spam complaints.

You always receive spam complaints when doing cold email campaigns, it's mathematical. You can't please everyone and there will always be people pissed off by your emails.

Even if you follow all the best practices, send relevant emails with a great copy. In 2023, without email warm-up, you'll suffer from landing in junk.

Below, two graphs of a sender reputation, with and without email warm up so you can better understand the differences :

a graph of a dropping sender reputation thanks to email warm up
Without email warm up, the sender reputation is falling
a graph of a positive sender reputation thanks to email warm up
With email warm up, the sender reputation is maintained

How to warm up your email account

There are two ways to do an email warm-up : automatically using an email warm up tool like MailReach or manually using your time and your friends, colleagues or family. Let's cover both ways in this section.

The automated email warm up

There are big benefits of using an automated email warm up service :

  • You save time and have nothing to do since it’s automated.
  • It's more efficient to build, maintain and repair your sender reputation.
  • It's faster to make your email account ready to send your campaigns. 14 days is enough VS 21 days minimum for manual warming.
  • A warm-up tool helps you monitor your sender reputation day after day. And you can't improve what you don't measure.
  • It’s a powerful solution to improve your deliverability and maintain it during your campaigns.
  • It gives better results on your open rates and in turn, better click, reply, lead rates.

To do a proper automated email warm up (let’s take the example of using MailReach) you basically have to connect your email account (the sending address) to MailReach and let it run for you in the back.

Once you have connected your email address to MailReach, it will start conversations with high reputation inboxes of MailReach’s network following a smart behavior.

The ramp up is gradual, the conversations are meaningful (which is important) and the most part of the emails sent are automatically opened, replied positively, markeed as important, removed from spam if needed.

The engagement rate generated by all these positive interactions will raise your sender reputation to maximize your deliverability. Isn’t that awesome? 😎

The manual email warm up

If you have time and are not ready to pay for an email warmup service, you can do a manual warm-up. Even if it’s less optimized and time consuming, it can do the job.

What you need to do a manual email warm-up

  • A list of email addresses you own with a good reputation and aged domains on various email service providers (Gmail, Outlook, etc).
  • If not, a group of friends, colleagues or family members ready to reply to your emails.

Warming up manually: the theory

Here’s what you need to know about doing a manual email warmup.

As said before, to build a positive email sender reputation when your domain or email address is new, you need to show the the email service providers that you’re a legit, interesting person who has “a lot of friends” with great reputation. You need to be the great Gatsby.

To demonstrate this, the best way to do an email warmup is to gradually send emails to high reputation inboxes and get engagement from them.

That means getting positive interactions: having your emails opened, replied, marked as important and removed from spam (if you landed in spam, which usually happens sometimes when your domain is new and “on probation”). That’s email warmup.

A high reputation inbox can be :

  • A professional address on an aged domain (2 years+) that manually sends normal business emails (no or very few campaigns) and, because of this use case, gets a lot of positive interactions.
  • An aged personal address used to send normal emails and get a lot of replies. Typically, your old personal Gmail or Hotmail account or the ones of your friends and family are good examples.

Voilà, it was the theory about manual email warm-up, now let’s see the practical steps.

Warming up manually: the practical steps

The first day, send around 5 emails to high reputation inboxes you own or owned by people you know and ask them to open the message, reply positively, mark as important and remove from spam if needed. The more positive interactions, the better.

The next day, send 10 emails following the same process.

The following days, increase the number of emails by add 10 daily until you reach 100 per day.

Depending on the daily volume you plan to send, increase the number of emails sent by adding 30% more daily until reaching your goal.

Success factors :

  • Prioritize to send emails to the inbox providers you're actually going to contact. If you reach out to professionals, don't send emails to, Hotmail or inboxes. Email warm up has to be done towards the inboxes that represent your targets.
  • Get as many positive interactions as you can to build a positive sender reputation.
  • When increasing the volume, make sure to have a linear growth curve. Avoid spikes, make it smooth.

How long does it take to warmup an email address?

If you use an email warm up service like MailReach to automate and optimize the process, 14 days are enough to warm up an email address with no history.

If you choose to do it manually, you need at least 21 days for a decent email warmup as it's less efficient.

Once you reach 14 days of automated email warm up or 21 days of manual email warm up, you can start sending emails on your end and gradually increase the the number of emails each day until reaching your daily goal.

For a cold emailing activity, we recommend:

  • Using an efficient email warm up tool to get the best results
  • To start warming without sending any campaign for 14 days
  • At Day + 15 (once you have passed the 14 days pre-sending warmup phase) you can start sending 50 cold emails / day and add 20 more emails each day until reaching maximum 150 / day per email account and ideally per domain.
  • No more than 150 / day to protect your reputation. Never send too many emails per day, it's a deliverability killer.

In addition, keep in mind that warming an email address is important before your campaigns but also during your campaigns.

Warming up only before your campaigns is not enough.

You can warmup an email account for 21 days, then stop the warm up, start your campaigns and land in spam 1 month after. Warming up only before your campaigns does not immunize you against the junk folder.

Maintaining a high engagement rate (getting your messages opened, read, marked as important, removed from spam) is what helps you stay away from spam during your campaigns.

More information here : Why to Always Keep Email Warming to Maintain a Great Deliverability

To get the best results, use a (really) smart email warm up service

Remember that not reaching 100% of your recipients means missing customers (and growth).

Think about it. If you don't have 100% of your emails reaching the inbox, that means a certain % of your messages never reach your recipients. You simply miss them because of spam. Wasted.

Using a proper email warmup solution improves your email deliverability and as a result, helps making more sales.

The ROI of doing email warm up on your email addresses is definitely worth it.

In 2023, sending cold emails has never been easier, but reaching the inbox and staying there in the long run has never been so hard. If you want the best ROI from your cold emails, you have to use an efficient email warm up tool.

Here are the 4 most important things you need to pay attention to when choosing your email warm-up tool.

1. Choose an email warm up solution that most closely replicates an interesting human

The warm up emails have to be meaningful

Most of the warming solutions use gibberish or "weird AI" content in the email conversations they generate. These messages don't make any sense.

There's a problem with that practice: the major inbox providers such as Google and Microsoft understand the content of your emails.

If you're exchanging gibberish messages, they don't understand it and it doesn't build trust with them.

In fact, Google and Microsoft are not able to suggest smart replies / suggestions on these “warm up emails”.

Compared to most solutions, MailReach emails are meaningful, human and emulate a cold email activity that gets positive replies to build more trust with the mailbox providers and spam filters.

Microsoft and Google are fully able to suggest smart replies on MailReach warm up emails (screenshot below).

an example of a warm up email by MailReach with smart replies suggested by Google
An example of a warmup email sent by MailReach

A solution that generates interested replies is more efficient

As said above Google and Microsoft understand the content of your emails. That includes understanding the replies you receive to your emails.

If you mostly receive replies saying "No, I'm not interested", "Stop", "Unsubscribe", then it sends a signal to the mailbox providers and spam filters that you send uninteresting emails.

On the contrary, if you receive many replies saying "Yes, I'm available for a chat", "I'm interested", "It would be great", then it sends a much more positive signal to the inbox provider that you're an interesting sender who deserves to land in inbox.

MailReach's email warmer makes you receive positive replies to your warmup emails. That's more efficient to build a strong reputation and increase your email deliverability.

2. Choose an email warm-up tool that uses a large number of human inboxes

As said earlier, to warm your email address, an automated solution will make it exchange emails with other inboxes to get positive interactions.

First, it is really important to make your sending address talk to inboxes that represent your targets.

In other words, if you mostly target professional inboxes in your campaigns, you should warm your emails mostly towards professional inboxes, not personal ones and vice versa.

On the contrary, if you only target personal mailboxes, then it's not relevant to warm up towards professional ones.

Why? Because professional mailboxes don't filter spam the same way than personal mailboxes.

Second, the warming tool should have a large number of real mailboxes. We recommend more than 10,000 and ideally with aged, high reputation domains.

Why? Because that means your address will talk and receive engagement from a high number of different mailboxes with domains that have more weight. That's more efficient to improve your email deliverability.

MailReach has a network of 15 000+ real (human) inboxes, including hundreds of high reputation aged domains. It definitely helps our customers have the best results for their inbox placement.

3. Choose a solution that helps you measure and improve your whole deliverability

A proper cold email deliverability solution should help you easily follow and improve two metrics : your sender reputation and the deliverability (inbox placement) of your own email campaigns.

Remember the formula: deliverability = sender reputation (inbox, domain, IP) + sending setup + content.

You can have a perfect sender reputation and still land totally in spam because of your content or sending setup.

You have to align 3 planets. And to do that, you need:

  1. To make sure your sender reputation is good (the role of email warm up)
  2. To make sure your content and sending setup don't lead you to the junk folder (the role of deliverability tests / spam tests)

A proper email warmer should help you measure your sender reputation towards Microsoft (Outlook, Office 365) and towards Google (Gmail, Google Workspace) as these are separate entities and use their own scoring system. You can have a great reputation with Office 365 and a terrible one with Gmail and vice versa.

Also, you should be able to check the deliverability of your own campaigns by testing your content and your sending setup. To do that, you need to run an email spam test.

MailReach offers a reliable spam checker tool to help you measure and improve the inbox placement of your own emails. That's super important.

MailReach combines smart email warming and a reliable deliverability checker to skyrocket your results

MailReach helps more than 3,000 companies reach the inbox of their recipients by combining smart email warming and deliverability tests. Our role is simple: help you maximize the results of your campaigns and stop missing customers because of spam.

By using MailReach, our customers get :

  • A 68% increase of open and engagement rates on average.
  • A 140% increase of deliverability score when using our email spam test.
  • A 17% increase in revenue from the deliverability improvement on their outreach campaigns.

Our experience:

We come from 7 years of intensive cold emailing and deliverability fixing for 130+ companies in 40 different industries:

  • We grew our previous company from 0 to $120K Monthly Recurring Revenue in 6 months.
  • Helped raise €56M in funding for IPOs and seed rounds with cold emails.
  • We get 75% open rate on average on our campaigns.

In short, we know the cold outreach and deliverability game like our pocket, you can count on us.

‍Final thoughts on email warm up

Reaching the inbox has never been more influenced by the engagement you receive (or not) on your emails.

In 2023 and more than ever, you need to have and maintain a high engagement rate on your sending activity in order to reach the inbox of your recipients and stay there in the long run.

As said earlier, you can do the email warmup on your own without using an email warm up service.

It can work, but it won't be as efficient as using a service dedicated to email warm up and maximizing your email deliverability.

As nowadays, email deliverability has become a science, that’s a complex set of skills, best practices and resources to master in order to land in inbox in the long term.

Sending emails is the easy part.

But sending emails that reach your recipients’ inbox is harder.

This is why using a deliverability solution such as an email warm up service is a precious help to get better results and also, get peace of mind.

MailReach is compatible with any inbox / SMTP

No items found.

More resources for your deliverability

Made with ❤️ and 🥖 in Paris, France 🇫🇷