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Why Perform an Email Warmup? – 5 Steps to Execute the Perfect IP/Domain Warmup

Warming up your IP/domain before sending an email.

Think of it as the stretching exercises performed right before you begin working out. If you workout with a warmup, the chance of injuring your muscles is much higher. And the same is the case with emails.
Running a full-fledged email campaign on an IP/domain that hasn’t been warmed up before can get a lot of your emails reaching the spam folder. And if you continue sending large email volumes without considering the warmup phase, you’re far more likely to get blocklisted.

But how do you warm-up your IP or domain? And what is the best way to do it? 

By the time you finish reading, you’ll know:

• Why is email warm-up necessary?

• Is it possible to skip the warmup phase and still send high volumes of emails?

• What are the steps to execute an email warmup?

But, what does this have to do with warmups?

See, email was never created to be a mass marketing tool. It was built for simple one-to-one communication. 

And when so many people started using it for marketing, that gave rise to spam. People no longer enjoyed checking their emails. 

So, mailbox service providers started implementing spam blocking mechanisms.

Fast forward to 2020. These spam filters are now highly sophisticated.

They are Artificial Intelligence-based algorithms that decide on the fly, which email deserves to be in the inbox, and which one deserves to be in the spam folder.

And they don’t trust a new sender immediately.

This is why email warm ups are necessary

When you start using email marketing or resume after about 30 days of not using email, your reputation with the algorithms needs to be built.

The algorithms do not know if your emails deserve to be in the inbox of users, even if 30-35 days ago, you were a great sender.

To build this trust, you start sending a small volume of emails and gradually increase the volumes.

This single line sums up what warming up an email is.

As these algorithms understand the type of emails you’re sending out, and that people are interacting and engaging with your emails, you start gaining their trust. 

And then when you start sending your complete volume of emails, these spam filters know your emails should be delivered to the inbox. 

So here’s a question – what does a mailbox service provider look at before deciding where your emails land?

There are multiple parameters that are taken into consideration, and these parameters vary between different mailboxes. But a few of those continue to stay the same between all of them. Here are a few known parameters that mailboxes use to verify that your email content isn’t spam:

• Subscriber engagement with your emails 

• Relevance of content with the subscriber’s general behavior

• Availability of authentication protocols

• Spam complaint rate

• Unsubscribe rate

Can you skip the warmup process and get the right to send emails?

Image Credit: Sergio Souza

You know you aren’t sending spam to your users. But the spam filtering algorithms don’t. 

And these algorithms are the gatekeepers. If they don’t know you, they will not let you in.

If you begin sending out large volumes of emails without warming up your IP and sending domain, you are highly likely to get dropped into their blocklist. 

The same applies if you resume email marketing after a month or more. The reputation that your IP and sending domain acquires is known to reset after 30 days of not being used. 

In such a case, if you begin sending out your regular email volumes, expecting that your reputation is intact, you’ll experience inboxing issues. So irrespective of your status before you paused your campaigns, it’s of utmost importance to ensure you maintain your reputation consistently with regular email campaigns.

If you have fallen trap to the reputation reset, you know that performing a warm-up every time is tiresome. To avoid this, we always advise our clients to use the heartbeat campaign technique

Even if you have paused your campaigns, you can continue to send out emails to a small bunch of engaged users so the next time you want to resume with higher volumes, you can skip the warm-up altogether.

It just saves you a lot of time. 

NOTE: If you’re using an email service provider and are on a shared IP address, your IP reputation will be maintained by your service provider. In such a case, you can resume sending emails without the warmup.

But if you have stopped emailing for a while and are using a dedicated IP (or an in-house setup), it’s highly recommended that you go through the entire warmup process before you begin sending out emails in bulk.

Let’s go over the 3 different ways to perform the perfect warmup for your email list 

How to Execute the Perfect Email Warmup Program?

The warmup process looks similar to the image above in terms of numbers.

1. Know your slabs and base numbers

Before you begin with performing a warmup, you need to know the numbers. 

  • How many users are you sending an email to?
  • How often will you send those emails?
  • When do you increase the number of emails that you send out?

If you’re using the image above with Pepipost’s warmup slabs, you are going to start with 500 emails on day 0. 

Once these emails are out, you can send the next set on Day 1, where the number of emails is 3000.

As you gradually increase the numbers, within 15 days you’ll be able to send out 200,000 emails per day. However, keep monitoring for inboxing and other relevant engagement metrics. Also, keep a keen eye for any spam complaints, especially on Google postmaster.

2. Segment your email lists

You can send out all the emails you want and your warmup program may still lead to failure. 

The purpose of a warmup is to show the mailbox provider, that your emails are relevant and that people are enjoying and engaging with them. 

The best way to do that is by sending your emails only to the most engaged users. 

By doing that, you ensure that your emails are well-received by the users who are on your sending list. 

And when a mailbox provider sees that people are engaging a lot with your emails, they start trusting your emails even more. 

3. Send your best content

This isn’t advice only for the warmup process, but for your entire email marketing plan. 

But it’s especially powerful during the initial phases. 

After you segment your users based on activity, you need to send them your best content. 

We want as many users to give their mailbox algorithms the signal that our emails are good. And this is possible when they interact, open, click-through, read your emails, and maybe even share them. 

4. Keep a track of what works and what doesn’t

You can’t grow what you don’t track.

When you are sending out these emails and taking all the precautions to ensure a great warmup program, you should track what you’re doing.

  • A few examples of the data points to track:
  • The content that generates the highest engagement
  • Email unsubscribers, and what triggered the unsubscribes
  • Spam reports if any
  • Average open rates and click rates across all your sent emails

These elements are your starting points to track the performance of your warmup campaign. 

5. Start sending your emails, and follow the plan

Stick to your plan. You may be tempted to start sending out your complete volume as soon as you begin seeing some good engagement. 

But no matter how well-received your content is, it’s best to gradually grow the numbers to avoid getting put into the spam folder. 

The more strictly you follow the plan you set for yourself, the better the results will be. 

Essentially, the entire process of a warmup is only to get your trust back up. And at a point where the receiving mailbox providers are unsure about your email content, it’s best to continue slowly. 

What to expect before, during, and after a warmup?

Consider this situation. You have a list of over 100,000 email subscribers and you haven’t sent them emails for quite a while now. 

In most cases, you can expect your email reputation to reset to neutral. And you don’t have an option to turn it on-off on-demand. 

Before the warm-up

When you start from scratch, your reputation is going to be low/zero. This is the same case if you have stopped emails for a while. 

At this stage, sending out a large number of emails will affect your inbox placement rate. So you can expect your inboxing to be in the low 50%s or even lower depending on how engaged your audience is, and your list targeting and segmentation.

This is normal and there’s nothing to be concerned about here. Once you begin with your warmup process, the inboxing will move upwards.

During the warm-up

One of the major changes that you’ll notice as you begin your warmup process is the drop in email inboxing during the initial phase of the warm-up

But that’s temporary.

As the mailbox provider algorithms understand your content and the engagement of their users with your emails, your sending reputation is built up. 

It’s a fairly quick process and the algorithms are smart enough to identify good emails. 

Once you build up enough reputation, the algorithms allow more of your emails to reach the inboxes of their users. Since the threshold for every mailbox provider is different, it’s important that you do not rush the process, and perform naturally variable email sending. You don’t have to fix a number and reach the goal every time. 

For example, if your daily cap is 10,000 and you don’t need to send any more than 9000 emails, that’s alright. You can stop right there. 

Our goal is to have an upper limit for each day while the email reputation is built up. 

After the warm-up

Once you’ve successfully performed a warmup, your inbox placement will have improved. Compared to the below 50% inboxing before warm-up, you can expect 70-90+% inboxing depending on how good your content was after the process is complete.

As more emails begin reaching your customer inboxes, the higher your chances of converting users. Even if your conversion rate remains the same overall, more people seeing the email will still result in higher absolute conversions. 

After a good warmup program, you can expect a statistically significant improvement in all of your email metrics combined.

Whenever we onboard a new client, they are automatically taken through the process as milestones to unlock further slabs. You can use these numbers as a reference.

Let’s begin with the warmup process. 

There are 5 factors for maintaining consistency during the warmup phase.

  • Know how many users you will send emails to in each slab
  • Segment your email lists based on their engagement and activity levels
  • Send relevant content that your users will fall in love with
  • Keep track of what works and what doesn’t
  • Start sending emails, and follow the plan

We’ll take a look at each of these points individually now.

Frequently Asked Questions Roundup

Let me answer a few questions that have been asked by a lot of people online. 


A proper email warm up program gives a significant boost to your first email campaign. Think of it as the trust building phase in real-world relationships. Until a person trusts you, you have limited access to their knowledge and resources. Similarly, mailbox service providers won’t let you access their subscribers without first trusting you. 

But once you build up the required trust, they’re happy to deliver more emails from you to their users because they know your emails are useful to their users. 

And remember these few points, before you send out an email: 

  • Know what’s relevant to your customers
  • Segment lists based on their preferences
  • Send them the best content possible
  • Keep a track of which emails work best, and which ones didn’t as well
  • Send more of the kind of emails that work best.

You can expect your performance to drop a little during the warm-up phases and that’s normal. Once the program is complete, you can bypass the deliverability issues for as long as you maintain the reputation you’ve gained. 

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