The Dos and Don’ts of Warming Up a New IP Address

James Miller
July 20, 2021
minute read

Email deliverability is a big deal. Every email performance metric suffers if your emails are dropping into people’s spam folders or getting blocked.

Your email deliverability relies heavily on your sending IP address reputation. When you use a dedicated IP address, that address gets a reputation score. Your IP address reputation is a bit like your credit score. It needs to be built intentionally and strategically. And it’s very difficult to repair your IP reputation if you damage it.

But, a new IP address has no reputation score. ISPs treat new IP addresses the way banks treat people with no credit: they’re very wary, and tend to be sensitive to missteps.

That’s why you need to properly warm up a new IP address. Internet service providers use the volume of emails, among other things, coming from your IP address to evaluate your IP address.

If a new IP address pops up and starts sending out tons of emails, that’s suspicious to ISPs. Spammers often hop from IP address to IP address and send a bunch of low quality emails until they get blocked.

Warming up a new IP address gradually increases the send volume from your IP address, and organically builds a good reputation with ISPs. This signals to ISPs that you’re a legitimate emailer, sending emails that people want to read. This way, your emails land in recipients’ inboxes.

So, warming up your new IP addresses is essential for achieving high deliverability rates and getting the best ROI from your email marketing program.

But, there are some nuances and best practices for warming up new IP addresses that you need to know before you start sending emails from your shiny new IP address.

Here’s the down and dirty on warming up new IP addresses.

Why You Should Warm Up Your IP Address

ISPs are tasked with stopping spam and scam emails from getting to your inbox. To do this, ISPs have protocols for evaluating email sending behavior.

When you fire up a new dedicated IP address, warming it up gives ISPs the chance to gather information about your email activity, and assess whether or not you’re a spammer.

There’s a broad range of factors that impact your IP reputation. ISPs look at things like:

  • Send volumes
  • Open rates
  • How people interact with your emails
  • Whether or not people move your emails to other folders
  • Undeliverable emails
  • Hard bounces
  • Spam complaints

All this data gives ISPs information about the quality of your email lists, the relevance of your emails, and how responsive your audience is. Your IP reputation is a product of all these factors.

When you first activate an IP address, there’s no established reputation. So, ISPs will very quickly downgrade the reputation if they detect suspicious sending activity. Additionally, activating an IP address and immediately sending tons of emails is viewed as suspicious activity, and will get your IP blacklisted quickly.

Warming up your IP address is how to prove to ISPs that you’re a legitimate email sender, and that they should send your emails to the inbox. Also, it establishes your sending patterns, which helps protect you in the event that your inbox gets hijacked, because ISPs can identify unusual email behavior and block strange emails.

The warm up process is also an opportunity for you to run A/B tests to identify your best emails and maximize the ROI from your email channel before you send emails to your entire email database.

What to Do During IP Address Warmup

There are two aspects to warming up a new IP address:

  • How many emails you send
  • What type of emails you send

How many emails you send helps you demonstrate legitimate sending behavior. The type of emails you send shows ISPs that you’re sending quality emails.

These two aspects of IP warmup minimize the risk of getting many spam complaints and bounces early in the life of your IP address, when the reputation is most vulnerable to irreparable damage.

Start with low volumes of high engagement emails. Transactional emails are best for warming an IP address. These are good transactional emails to use for email warmup:

  • Purchase receipts and thank you emails
  • Account creation emails
  • Password reset emails
  • Account notifications

These emails get the best open and engagement rates, which signals to ISPs that you’re sending relevant emails, and that your audience is receptive to your messages. Send these emails for a few days before jumping into your marketing emails.

For your marketing emails, build out a schedule for ramping up to full send volume over the course of 15 to 60 days. Monitor your engagement metrics as you ramp up your send volume. Keep an eye on:

Follow the best practices of email writing to keep your email engagement high during the warm-up period (and after). Also, ensure that your email authentication is set up properly before you start warming up your IP address.

Also, monitor your reputation and check blacklists to see if you’ve had any issues that damaged your IP reputation. There’s a handful of useful tools for tracking your sender reputation and blacklists:

WIth these tools you get a two-pronged monitoring approach that tracks your email performance internally—through your email service provider—and you can see how much your email engagement is affecting your IP reputation externally—in the DNS records and blacklists that ISPs look at.

Email Deliverability: The Ultimate Guide to Keep Your Emails Out of the Spam Folder
View Guide

How to Warm Up an IP Address

The easiest way to warm up a new IP address is to use an IP address warm up tool from your email service provider. Otherwise, you’ll have to step up your send volumes manually, which is too time and effort intensive to be practical.

Most quality email service providers have email warm up services, like the warm up mode in Rejoiner 2. Warm up mode automatically increases your send volume on a daily basis, per ISP, according to your target volume.

As we mentioned earlier, the warm up timeline is between 15 and 60 days. The length of your IP warming period depends on your ultimate email volume. There are variables—like the average number of emails you send each person on your list—but it’s best to follow a linear warm up process for the first 15 days.

An ideal warm up schedule is to roughly double your send volume each day until you reach your target daily sending volume. It takes a little math, but you’ll need to calculate your daily sends so that your send volume on day 15 of your warm up period is a significant portion of your total sending volume.

After day 15, you can simply double your daily send volume until you’re maxed out. This can usually be completed in 30 days or less. You’ll only need to extend the warming period to 60 days if your email volume is ultra high.

Most internet service providers won’t even notice your emails until you’re sending about 100 emails per day. So, once you’re ready to start your IP warming process, you can start with 100 emails on your first day, and schedule your daily sends so you hit your target email volume on day 15.

If your email service provider offers an IP warm up service, they’ll take care of the math for you.

Here’s a sample IP warm up schedule to show how your email volume should ramp up over the first 15 days. Your daily warm up volumes will be different if you’re sending less than 1,000,000 emails. But you can see how the send volumes ramp up.

Email is an incredibly powerful marketing channel. But, it only works if your emails actually reach customer inboxes.

If you follow a warm up schedule like this one, you’ll protect the reputation of your email sending infrastructure, maximize your deliverability, and get the best the ROI from your email marketing.

What to Do Now

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James Miller


James Miller is a content writer at Rejoiner. He's responsible for engaging with customers through the Rejoiner blog. He researches and writes articles that are useful for customers and subscribers. James is a ski nerd and book writer.

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