IP Warming: What Is It?

Internet protocol (IP) warming refers to the practice of slowly scaling up the marketing emails you send to your mailing list in order to build trust with your users’ internet service providers (ISPs). 

This is important whether you’re just starting to send content to a new mailing list, or whether you’ve moved an existing list to a new IP address.

If you don’t take the time to warm up your IP and send a sudden, high volume of emails, your users’ ISPs may filter your messages into spam or even block them entirely, negatively impacting your deliverability. This article will look at how to effectively warm your IP in order to deliver email marketing campaigns at scale.

Why Email Marketing?

Email marketing is still one of the most effective strategies for reaching and engaging with your customer base, with average open rates ranging between 18% and 22% (according to Kinsta). Email marketing also has a very high ROI, averaging a $42 return for every dollar spent (according to Campaign Monitor). 

Email marketing is even more effective as a component of a cross-channel marketing strategy, using marketing automation to integrate a drip email campaign alongside messages through other channels, including SMS messaging, push notifications, in-app notifications and direct mail. 

But, in order to ensure that your email marketing can make an impact as part of a cross-channel strategy, deliverability is a key concern. If your email address doesn’t have a high “sender reputation,” many ISPs could begin to blocklist your email address, blocking the messages or sending them to your users’ spam folders, even if they’ve opted in to receive your emails.

Building Your Sender Reputation

Your sender reputation is based on a number of factors, including how many emails bounce, how many spam complaints you receive, how many unsubscribes you get, and your email frequency. Your email domain is factored in as well. Even if the email address you are currently using hasn’t been flagged, if others on the same domain are guilty of poor email marketing tactics, you may still be blocklisted.

In order to avoid getting blocklisted, it’s important to dedicate one email address per domain to sending messages to your mailing list. You should also ensure that all email addresses collected are opt-in (preferably double opt-in), and make sure your subscribers understand the frequency of emails they’ll receive. 

Even following these best practices, you still may find your emails going into spam folders or getting blocked if you start emailing your entire list at once. That’s where IP warming comes into play.

How IP Warming Works

IP warming works by sending out emails to your list in low volumes over a period of weeks, only gradually scaling up to full capacity after you’ve had the opportunity to build a positive sender reputation.

First, make sure that your list is “clean,” made of only authentic subscribers who’ve intentionally opted in to receive your communications. You can use an email validation service to scan through your entire mailing list and identify any spam traps, bots or other invalid emails that are likely to bounce, cause spam complaints or remain unopened. 

Next, start by sending a small volume of up to 5,000 total subscribers, beginning with your most engaged customers. Focus on those who’ve recently signed up for your list, or those who’ve recently made purchases. There is a high likelihood they will open the emails and a low chance they would unsubscribe or report as spam. From there, you can increase your sending volume every three to four days.

Monitor your email performance as you warm your IP. If you start to see deliverability problems such as bounces or spam reports with a specific ISP, halt on sending messages to that ISP for the time being, audit the cleanliness of your lists and troubleshoot before you continue sending them.

You should be able to continue growing your send volume over a period of approximately four to six weeks. Then,you should be able to safely email your entire list at once. Before doing so, ensure that you’re seeing a high rate of deliverability at each phase, and halt on adding to your list until your deliverability rates go up.

Best Practices for Onboarding

To ensure your subscribers engage with your content and help you build a positive sender reputation, make sure that you’re following email marketing best practices such as:

• Send from a familiar address. Make sure your domain name matches your brand name so your subscribers will be able to easily identify who the message is coming from.
• Avoid using a misleading headline. There’s time to be clever later, but when you’re in the early stages of establishing your email list, focus on using simple headlines, such as “Welcome to [brand]”, or “Your [brand] subscription,” so subscribers know what to expect.
• Make sure subscribers understand how and when you’ll communicate with them. Even if subscribers have opted in, it’s important to make sure their expectations are in line with the communications they’ll receive. Provide multiple options for communication frequency (i.e., daily or weekly) and allow them to opt in or out of different types of messages, such as promotional offers. 

Email Marketing as Part of a Cross-Channel Marketing Strategy

By taking the time to validate your email list and follow IP warming best practices as you onboard your email list, you’ll be able to build your sender reputation and ensure maximum deliverability. 

Once you have a strong, engaged email list, you can utilize it as part of an effective cross-channel marketing strategy. You can develop highly personalized campaigns across multiple channels that reach customers based on their preferences with content that’s dynamically generated based on their unique interests, behavioral patterns and purchase history. 

Using a cross-channel marketing platform like Iterable can help you scale your marketing strategy across email and all of your other channels, optimizing content and channels automatically to meet your customers with the content and format they’re most likely to respond to, helping to drive high engagement and conversion rates.