What is IP warming and why it matters for email marketing

In any relationship, jumping in too fast can raise red flags – while a steady, deliberate approach builds credibility. In the same way, gradually establishing trust between your internet protocol (IP) and Internet Service Providers (IPS) is essential for effective email marketing.

This is where IP warming comes in—a process designed to introduce your emails to ISPs at a slow and steady pace so you can earn a solid reputation for high deliverability.

In this blog, we’ll be discussing the importance of IP warming, how Internet Service Providers (ISPs) and Mailbox Providers (MBPs) play distinct roles in email deliverability, and the essential steps you need to take to build a strong sender reputation for long-term marketing success.

Why your IP Reputation Matters

Studies show that 57.8% of Google emails land in the inbox, and 37.74% in the promotions tab.

IP warming is necessary when using new IP addresses, reactivating an IP that hasn’t been used for a while, or when switching domains. In these cases, sending a high volume of emails immediately can lead to poor deliverability and long-term damage to your sender reputation. Warming ensures the IP is trusted by ISPs, ensuring better email performance over time.

A poor reputation, resulting from high bounce rates or spam complaints, can severely limit your reach, leading to reduced inbox placement. On the other hand, maintaining a positive sender reputation boosts deliverability over time.

Building Trust with ISPs Through Gradual Warm-Up

Half of marketers say that email marketing is their most impactful channel. With 4.48 billion email users worldwide, email is an incredibly powerful tool for engagement.

By focusing on steady growth rather than abrupt spikes, you can ensure that ISPs view your emails favorably, leading to better inbox placement in the long run.

But before we get into how to initiate IP warming, it’s important to understand the roles that Internet Service Providers (ISPs) and Mailbox Providers (MBPs) play in the process.

Understanding the Role of ISPs and Mailbox Providers in Email Deliverability

While both ISPs and MBPs influence email delivery, MBPs are the primary focus during IP warming as they control inbox placement and sender reputation.

ISPs: The Transport Layer of Email Delivery

ISPs, like Verizon, Comcast, or AT&T, are responsible for managing the transmission of emails over the internet. Think of them as the road your emails travel on to reach their destination. While their role is mostly focused on safely delivering emails, ISPs can also impose security measures. They scan for spam, viruses, and other malicious content to prevent harmful emails from spreading across their networks.

In some cases, ISPs can block emails from suspicious IP addresses entirely or throttle (limit) the volume of emails sent from a particular IP, especially if it's new or sending a large volume of emails too quickly. However, ISPs do not decide where your emails end up—whether in the inbox, spam, or promotions tab. Their main job is to ensure the safe transport of your emails to the recipient's Mailbox Provider.

MBPs: The Gatekeepers of the Inbox

Once your email passes through the ISP, it lands in the hands of the recipient's Mailbox Provider (MBP)—this is where the real decision-making happens. MBPs, such as Gmail, Yahoo, and Outlook, are responsible for filtering and sorting emails, ultimately determining whether your email reaches the inbox, promotions tab, or spam folder.

Mailbox Providers assess several key factors when deciding where to place your email:

• Sender Reputation: MBPs evaluate the reputation of the sender’s IP address based on past email performance, including bounce rates, spam complaints, and overall engagement.
• Authentication: MBPs check if your emails are properly authenticated using protocols like SPF, DKIM, and DMARC. Proper authentication improves trust and credibility.
• Content and Engagement: MBPs look at how recipients interact with your emails. High engagement signals a positive reputation, while low engagement or high spam complaints can harm it.
• Blacklist Status: MBPs also monitor whether your IP or domain is on any blacklists, which could cause your emails to be sent directly to the spam folder.

During IP warming, MBPs play a critical role in building your sender reputation. By gradually increasing your email volume and sending to highly engaged users first, you demonstrate to MBPs that your emails are trustworthy, which helps improve deliverability over time. The next section shows you how to do just that.

Step-by-step Guide to IP Warming

Let's dive into the practical steps you can take to improve your email deliverability over time, starting with preparing your email list.

1. Prepare Your Email List: Hygiene and Segmentation

Before starting the IP warming process, it’s crucial to ensure your email list is clean and well-segmented. List hygiene involves removing inactive subscribers, correcting errors in email addresses, and maintaining updated contact information to reduce bounce rates and spam complaints.

Segmentation, on the other hand, allows you to target your most engaged subscribers first, gradually introducing your emails to less active segments over time. This approach improves engagement rates and helps build a strong sender reputation during the IP warm-up process.

Here’s how to clean and segment your email list:

1. Remove Inactive Subscribers: Identify users who haven’t engaged in a long time (e.g., 6+ months). Consider a re-engagement campaign before removal.
2. Correct Invalid Emails: Use email verification tools to detect invalid or outdated addresses.
3. Remove Hard Bounces: Take out any emails that bounced due to invalid addresses.
4. Segment by Engagement: Start by grouping subscribers based on open rates, clicks, and engagement frequency.
5. Segment by Preferences: Organize based on demographics, purchase history, or other relevant data.

Regularly maintaining these steps keeps your list clean and boosts engagement.

2. Implement Email Authentication Protocols: SPF, DKIM, and DMARC

To protect your email campaigns and improve deliverability, it’s important to implement email authentication protocols like SPF, DKIM, and DMARC. These protocols verify that your emails are coming from an authorized sender, reducing the risk of phishing or spoofing.

Here’s how to implement SPF, DKIM, and DMARC protocols:

1. Consult Your Email Provider: Obtain the necessary SPF, DKIM, and DMARC values

2. Access DNS Management: Log into your DNS provider’s management platform

3. Add SPF Record:

• Create a new TXT record.
• In ‘Name’, enter your domain, and in ‘Value’, add the SPF value.

4. Add DKIM Record:

• Create a new TXT record.
• In ‘Name’, input the DKIM selector.
• In ‘Value’, paste the DKIM public key

5. Add DMARC Record:

• Create a new TXT record.
• In ‘Name’, enter "_dmarc", and in ‘Value’, input the DMARC policy.

6. Save Changes: Save each record and wait for DNS propagation (up to 48 hours).

3. Gradually Increase Email Volume

When warming up a new IP, gradually increasing your email volume over 4-8 weeks helps build trust with ISPs. Here's a basic framework:

• Week 1-2: Send to your most engaged subscribers (5-10% of total list). Aim for 500-1,000 emails daily.
• Week 3-4: Increase volume by 50-100% each week.
• Week 5-6: Continue scaling up to 50-60% of your list.
• Week 7-8: Gradually reach full sending capacity.

Throughout the first 8 weeks, monitor key metrics like bounce rates, open rates, and complaints to ensure positive performance, and make adjustments based on results.

4. Create Engaging Content for Effective IP Warming

Creating engaging content is essential to maximize open rates and clicks during the IP warming process. Focus on personalized subject lines, clear calls to action, and valuable, relevant content tailored to your audience.

Here are some Knak tools you can tap into to enhance subject lines, CTAs, and email content:

1. Knak AI: From crafting compelling subject lines and preheader text to generating accessible alt text, Knak’s AI tooling ensures your emails are effective and inclusive.
2. Knak Dynamic Content: This allows you to tailor each email to the individual recipient based on their preferences, behaviors, or demographics, making your messaging more impactful.
3. Knak Email Testing: Knak provides comprehensive email testing tools to guarantee your emails look great across all devices, helping you deliver a seamless experience to your audience.

These tools can improve the effectiveness of your email content, driving higher engagement.

Common Challenges in IP Warming

Even with the best preparation, IP warming can come with its challenges. Let’s explore some common obstacles you might face during the warm-up process and how to effectively address them.

Managing Bounce Rates: Keeping bounce rates low during IP warming is essential for maintaining a positive reputation. Focus on sending to verified, engaged email lists and remove invalid or inactive addresses promptly.

Dealing with ISP Blocking and Rate Limiting: If you encounter ISP blocks or rate limits, reduce your sending volume and pause the warm-up temporarily. Adjust your strategy based on ISP feedback to restore trust.

Monitoring and Adjusting Your Strategy: Continuously track performance metrics like engagement and deliverability. Adjust your email volume, content, and sending schedule to address any emerging issues proactively.

Tools and Services for IP Warming

There are several automated tools that simplify the IP warming process, helping you scale gradually while maintaining deliverability.

Automated IP Warm-Up Tools:

• SparkPost: Offers automated IP warm-up with real-time insights and reporting to track performance.
• SendGrid: Provides a structured IP warming tool, ideal for scaling email volume with both transactional and marketing emails.
• Twilio: Includes built-in IP warm-up services as part of its email API, allowing gradual scaling while monitoring engagement metrics.

Email Verification and Hygiene Tools:

• ZeroBounce: Removes invalid emails, detects spam traps, and ensures list accuracy.
• NeverBounce: Verifies email lists in bulk, flagging addresses likely to bounce.
• BriteVerify: Offers real-time email verification to keep your list updated and accurate.
• Kickbox: Provides detailed email verification reports, helping maintain a clean, engaged list.

These tools help ensure your list is primed for successful IP warming.

Deliverability Testing Platforms

• Sender Score by Validity: Offers a comprehensive score to measure the health of your email reputation.
• MXToolbox: Provides detailed insights into IP reputation and blacklist status.
• Mailgun: Monitors inbox placement and provides deliverability analytics.

These platforms help ensure your emails reach the inbox while maintaining a strong IP reputation.

How IP Warming Supports Cross-Channel Marketing

IP warming can play a critical role in a broader cross-channel marketing strategy. By ensuring that your emails reach the inbox and avoid spam filters, it sets the foundation for engaging customers across multiple channels.

For example, SMS and email can work in tandem to reinforce marketing messages. You can send a promotional email followed by an SMS reminder, enhancing engagement through multiple touchpoints. Email warms up the relationship, while SMS provides immediacy. Similarly, social media and email can complement each other, with email campaigns driving traffic to social media platforms, and vice versa.

As trust is established through IP warming, push notifications can also be integrated. These real-time updates can drive immediate engagement, particularly for transactional or time-sensitive content. By combining these channels, marketers can create a seamless customer experience, where each touchpoint reinforces the next, ensuring higher overall engagement.

Cross-channel integration also enables more personalized marketing efforts. The insights gained from email interactions—like open rates, click-throughs, and engagement—can help tailor SMS or social media outreach.

Balancing Marketing and Transactional Emails: Managing Both Streams During the Warm-Up Process

During the IP warming process, it's important to balance both marketing and transactional emails. Transactional emails—like order confirmations and password resets—are typically expected by the recipient and have higher engagement rates, which can positively impact your IP reputation. However, you must carefully manage the volume of marketing emails to avoid overwhelming ISPs early on. Start with smaller, engaged segments for marketing, while keeping transactional emails steady, ensuring smooth inbox placement for both streams as you warm up your IP.

Here's how to effectively balance both streams:

1. Leverage Transactional Emails: Transactional emails, such as password resets, shipping notifications, and purchase confirmations, are often opened immediately. During IP warming, maintain a steady stream of these emails to build positive engagement metrics. Since these emails are typically time-sensitive and relevant, they help increase positive signals like high open rates, low bounce rates, and minimal spam complaints.
2. Segment Your Marketing List:Start by sending marketing emails to your most engaged users—those who regularly open and click on your emails. These users are more likely to interact with your content, leading to higher engagement rates, which builds trust with ISPs. Gradually increase the number of recipients as your IP warming progresses, scaling from small, engaged segments to larger audiences.
3. Monitor Volume and Frequency:For both email streams, avoid sudden spikes in volume. Too many emails too quickly—especially for marketing campaigns—can overwhelm ISPs and negatively impact your sender reputation. Keep transactional emails steady and predictable, while slowly increasing marketing emails over time.
4. Analyze Performance Metrics:Keep a close eye on key metrics like bounce rates, open rates, click-through rates, and spam complaints for both marketing and transactional emails. Adjust your strategy as needed, ensuring that ISPs recognize you as a trusted sender.
5. Use Different Domains or Subdomains:To further protect your sender reputation, consider sending transactional and marketing emails from different IPs or subdomains. This approach helps prevent any potential issues with one stream from affecting the other.

Balancing these two streams allows you to build a strong sender reputation, ensuring both your marketing campaigns and transactional messages consistently reach recipients' inboxes.

IP warming is an essential process for ensuring long-term email deliverability and building a positive sender reputation. By gradually increasing email volumes, maintaining proper list hygiene, and implementing authentication protocols like SPF, DKIM, and DMARC, you can establish trust with ISPs. While challenges such as managing bounce rates and ISP limitations may arise, the right tools and strategies will help you overcome them. With a well-warmed IP, your marketing campaigns will benefit from higher inbox placement and better engagement, ultimately driving more effective cross-channel communication.

Ready to take your email strategy to the next level? Work with Knak’s powerful platform to simplify IP warming and streamline your email deliverability process. Get started today and build smarter, more effective campaigns!