Get Email Deliverability Right: Your Guide to IP Warming


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If you have a new IP address, you need to take on IP warming activities. Here’s how to do it and why it matters.

It’s officially fall, and that means it’s marathon season. In cities all over, thousands of people are lining up for the opportunity to run 26.2 miles.

If you’re pausing to wonder why people willingly do that, you’re not alone. Frankly, we’d rather just observe — and so we have. We’ve observed as some of our colleagues have spent the last four months training for marathons, getting themselves used to running seemingly insane distances so that they’ll be ready for the real thing.

And in fact this training process turns out to be quite similar to another “training process” that’s near and dear to our hearts: IP warming.

What is IP Warming?

IP warming is the process of “training” a new IP address in order to build a good sender reputation with Internet Service Providers (ISPs).

Specifically, IP warming requires you to regularly send emails from a new IP address and to gradually increase the volume of those emails. Much like the process of training for a marathon, you can’t go from zero to 26.2 overnight — you have to build up to that point by training ISPs to recognize your IP address as a good sender.

Why is IP Warming Important?

If you care at all about email deliverability (and you should), then IP warming is of utmost importance. You see, IP warming is necessary because we live in a world of spam and phishing emails. In this world, ISPs recognize that more often than not, emails from new IP addresses are unwanted (or even dangerous) and are coming from senders who have been blacklisted on previous IP addresses.

IP warming is the process of letting ISPs know that you’re one of the senders who are actually welcome in people’s inboxes. As a result, if you want to make sure you have a good sender reputation so that you can (a) send high volumes of emails and (b) stay out of the spam folder, then you need to engage in IP warming for any new IP addresses.

How Do You Handle IP Warming?

So how exactly do you go about IP warming in order to build a good sender reputation and ensure email deliverability?

The IP Warming Process

The IP warming process requires you to gradually increase the number of emails you send in order to establish a good sender reputation and ensure deliverability. In order to achieve these goals you need to:

  • Move from recipients’ spam to their inboxes
  • Garner email engagement like opens and clicks
  • Get the ISP accustomed to large volumes of emails coming from your IP address

Given all of these needs, the IP warming process should start small. Let’s say you have 20,000 email addresses in your database. When doing IP warming, your sends might look something like this:

Send 1 = 100 emails
Send 2 = 200 emails
Send 3 = 450 emails
Send 4 = 1,000 emails
Send 5 = 2,500 emails
Send 6 = 6,000 emails
Send 7 = 13,000 emails
Send 8 = 20,000 emails

The idea behind it all is that you are warming up your IP address in the eyes of the ISP. Going back to training for a marathon, you can’t start out running ten miles a day if you’ve never run before. You need to get your body used to the distance. IP warming is similar in that you need to demonstrate to ISPs that you can send 200 good emails (meaning you get engagement from recipients) before the ISPs will let you send 450 emails without landing in the spam folder. It’s the combination of regular, incremental increases in send volume on your end and consistent, positive engagement on your recipients’ end that will give you the sender reputation and deliverability you want.

IP Warming Dos and Don’ts

As illustrated above, the IP warming process isn’t very complicated. That said, there’s a lot of strategy that needs to go into those sends. To help you determine who to send emails to during the IP warming process and how to send them in order to ensure success, we’ve compiled our top IP warming top do’s and don’ts:


  • Be consistent: When you first start IP warming, your emails may very well end up in spam folders. Ideally, recipients should mark the emails as “not spam” and engage with them. This engagement will help you build a good sender reputation and will allow you to send higher volumes of emails without getting marked as spam. As a result, you should start with your most active and engaged users.
  • Ask for permission: As is always the case with email marketing, you need to follow anti-spam laws, like CAN-SPAM. In general though, asking recipients for permission to send them emails by requiring them to opt-in is a good way to ensure that your emails are welcome and will receive engagement. In turn, this engagement should help your IP warming activities go smoothly.
  • Throttle your speed: In addition to gradually building up the volume of emails you send, you should also pay attention to the speed at which you send emails. For example, you might not want to send 200 emails at once, but rather space the sending of those 200 emails out over a few hours. Over time, you can increase your speed alongside your volume.


  • Purchase lists: IP warming is in large part about blocking spammers, and that means ISPs pay attention to whether or not recipients want your emails as determined by their level of engagement. When you purchase lists, you may be hitting people who have never even heard of you and may not want to hear from you. When it comes to IP warming and email marketing in general, growing your database organically will serve you much better.
  • Move too quickly: Once again, a big part of IP warming is engagement with your emails, as that’s how ISPs determine whether or not recipients welcome your emails or view them as spam. Therefore, you need to pay attention to engagement as you consider when to increase your volume. You may very well find that you need to keep your volume at the same number for several days before you have enough positive engagement to move on to the next stage.
  • Get nervous about early failures: Because spam and phishing emails are so prevalent these days, ISPs approach new IP addresses very cautiously (hence the need for IP warming in the first place). As a result, mail from new IP addresses often gets marked as spam at first, so it may take a few tries before you start to see positive results. It’s important to keep in mind that this is normal. To help keep the process moving, you might ask users to check their spam for any emails from your business and to add you as a known contact to avoid having your emails go into the spam folder in the future.

Remember IP Warming is a Marathon, Not a Sprint

If you run a successful IP warming exercise, then you will also establish a good sender reputation. Going forward, this sender reputation will continue to affect your email deliverability, so it’s important not to throw away these best practices once your IP warmup is complete.

Long term, be sure to keep your database clean by conducting regular cleanup exercises that remove inactive email addresses and email addresses that don’t engage with your emails. At the end of the day, whether you’re IP warming or not, you should always prioritize engagement because that engagement is good for deliverability and maintaining a positive sender reputation, but it’s even better for your business.

Malinda Wilkinson
As Chief Marketing Officer, Malinda oversees all aspects of marketing including branding, messaging, lead generation, events and operations. She is passionate about B2B marketing and building relationships, programs and analytics to improve the value marketing delivers to an organization.


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