IP Warming: What Is It and Why You Need It

IP Warmup: What Is It and Why Do You Need It
Valeriia Dziubenko Valeriia Dziubenko 24 august 2023, 08:12 2237
For beginners

IP address warmup is an important procedure that helps you establish a good reputation for a new IP or an IP that hasn't been used for some time. Read about its best practices and learn why it's important.

What Is IP Warming?

What Is IP Warming?

When you try to send a large number of emails from a previously unused IP address, the chances are high that your messages will be rejected, even if there’s nothing wrong with the email itself. This happens because only reputable IPs are allowed to send large email campaigns; if an address shows a sudden increase in volume, email reputation services consider it as a spam source. Through IP warming, you construct a positive reputation for a sender address, based on its mailing history. The essence of the process is to gradually accustom the reputation scoring services to large volumes of emails while maintaining a low number of complaints on spam. As a result of the IP address warmup, the email delivery percentage also increases.

It is just the same as with sports — you don’t start a marathon all at once, first you’ve got to do a little warm-up.

Warmup Types

There are two polarized opinions on how a company should warm up an IP — one is for those who like to experiment and the other is for those who prefer a practical approach.

Manually Warm Up Your IP

This method is based on a gradual increase in the number of emails sent from one IP address. At first glance, this process seems pretty straightforward.

Manually Warm Up Your IP

The warmup usually takes somewhere from 15 to 60 days, depending on your desired email volume. You will need to extend the warmup period only if your email volume is very high.

Most internet service providers won't even notice your emails until you send about 100 emails a day. Thus, 100 to 500 emails on the first day is a safe volume to start with.

The basic IP warmup schedule routine is to roughly double the volume every two or three days until you reach the target daily volume. It requires a bit of math, since you need to calculate your daily amounts so that your last day’s emailing is a significant part of your total desired volume.

During IP warmup, you should always keep an eye on your delivery and bounce rates – if something goes wrong, it’s best to keep the number of messages unchanged for a few days.

Automated IP Warmup

With this method, the entire process of your the sender's IP warmup will be carried out by email service specialists. They will coordinate the specifics of the sender's business, and they help to go through all the stages, eliminating any possible risks. Warmup procedures orchestrated by ESPs usually include advanced strategies, such as automatic volume adjustment for each recipient’s domain on a per-hour basis.

IP Warming Best Practices

Before starting the warmup process, you have to make sure that your initial setup is correct. Here’s what you might need to do if you haven’t done it yet.

1. Set up digital signatures. SPF, DKIM, and DMARC records are a must, regardless of your provider. SPF confirms that the sending server is allowed to send emails on behalf of your domain, and DMARC tells ISPs what to do if the email does not pass verification.

2. Accumulate loyal customers. Such users are unlikely to mark your emails as spam, which is important when warming up a new IP. If you haven’t contacted them for a while, then refresh and reactivate the subscribers. Email service providers recommend that you should have no more than 10% of inactive addresses. Also, your ESP may require you to confirm the source of the subscriber base, so be careful and don’t start your campaign if the contacts have been gathered without users’ consent.

3. Prepare a neutral email. It would be a bad idea to start off with a selling email right away, so try making it more useful and interesting for readers — this way people will have fewer reasons to complain. For example, you can send a welcome letter with a promo code. Also, make sure that there is a valid unsubscribe link in the email. There’s no reason to hide it. If the Unsubscribe link is not clearly invisible, then the client is more likely to click on the «Report spam» button which will harm your reputation.

Why Some ESPs Don’t Perform IP Warmup?

ESPs usually require a warm-up procedure only if you purchase a new dedicated IP address for your mailings. By default, email service providers give their clients shared IP addresses that they have been using for years. These addresses have already been warmed up and have a high reputation score. It’s like a friendly neighborhood that you’ve recently moved to — the house looks good, the neighbors are smiling, the roads are smooth.

And it might feel good not to worry about all the warming up since you’re happy with the setting you have. However, when using this type of IP, you also have to share the downsides. The neighbors’ bad behavior affects the entire IP’s reputation, meaning it affects you too. There’s always a chance that a user-next-door abuses the service to send out spam.

What if I Don’t Have Time to Warm IPs?

What if I Don’t Have Time to Warm IPs?

Let’s put it plainly: you’ve got to consider the need for IP warmup in all cases which affect your sender reputation, like the following:

  • transferring email activity to a dedicated IP;
  • implementing email marketing for a new business;
  • changing the corporate domain.

Sudden mass mailings from a new IP may arouse suspicion among mailbox providers because there are no statistics on complaints from users about the new IP yet. In addition, when a new website is mailing thousands of addresses, some might ask — where did they get so many subscribers? Is it possible that they bought those addresses on the black market to send out spam? For this reason, so as not to take risks, email providers can mark these mailings as spam. And building a good reputation once again might take much longer than a couple weeks of warmup.

How to Limit Mailing Volume During Warming?

Most email service platforms allow users to segment their customer base and limit the number of users for the email address warmup. As the sending goes on, you can slowly adjust the number of subscribers who will get emails via new IP.

Subdomain Segmentation

There’s a good saying — don't put all your eggs in one basket. Send transactional emails and mass mailings from different subdomains, and this will help you avoid problems.

Let’s imagine a store that has been sending the same newsletter from four different subdomains, you know, just in case. One of these four domains got hacked, and the attackers used it to send out a fraudulent campaign «Congratulations, you won $100 000!». Most users immediately put these emails to spam, and the subdomain’s reputation is ruined. But thanks to three other subdomains, this little accident does not destroy the store’s whole email marketing.

Thus, a successful IP warmup relies on subdomain segmentation as well. Consult your domain registrars for further instructions on how to set up subdomains for the main domain.


Let’s do a quick recap:

1. Email providers monitor the sender’s reputation. If it is good, the letters get into the Inbox, and if it is bad, they end up in Spam.

2. By warming up the domain or IP, you can build a good reputation from scratch. Providers approve of this tactic.

3. Before you start your warmup, set up digital signatures, clear the database of inactive addresses and prepare a letter with a clearly visible unsubscribe link.

4. Start with a small number of emails and gradually increase the volume of mailing.

5. Send emails from several subdomains, this way you will isolate their reputation scores.

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