IP Warmup

IP warmup is a crucial process in email marketing that involves gradually increasing the volume of emails sent from a new or underused IP address. This gradual ramp-up is essential to establish a positive sender reputation with Internet Service Providers (ISPs), thereby improving email deliverability and avoiding spam filters.

How IP Warmup Works

When a new IP address begins to send emails in large volumes, ISPs may flag this sudden surge as suspicious, potentially categorizing the emails as spam. IP warmup mitigates this risk by slowly building up the email volume over time, allowing ISPs to become familiar with the new IP and trust the legitimacy of the emails being sent.

Implementation Examples

Step-by-Step Warmup Plan

Implementing an IP warmup strategy involves a systematic approach to escalating email volume. Here’s an example of a typical warmup schedule:

  • Day 1-2: Send 50 emails
  • Day 3-4: Send 250 emails
  • Day 5-6: Send 500 emails
  • Day 7-9: Send 2,000 emails
  • Day 10-12: Send 5,000 emails
  • Day 13-15: Send 10,000 emails

The gradual increase gives ISPs time to evaluate the sending behavior and user interactions (such as opens and clicks).

Sending to Highly Engaged Recipients

During the IP warmup phase, it’s crucial to send emails to your most engaged subscribers—those who regularly open and interact with your emails. This positive engagement improves your sender reputation more quickly.


<!-- Targeting Engaged Subscribers -->

if subscriber.status == "highly-engaged" {

  sendEmail("Exclusive Offer Just for You", exclusiveOfferContent);


Interesting Facts

  • Timing Matters: The IP warmup process typically spans 30 days, but the exact duration can vary based on the sender’s email volume and engagement rates.
  • Established ISPs Policies: Major ISPs such as Gmail, Yahoo, and Hotmail have explicit policies and thresholds for new IP addresses to control email volume and maintain user safety.
  • Reputation Tracking: Tools like Sender Score by Return Path or BarracudaCentral can help monitor and track your IP’s reputation throughout the warmup process.

Additional Information

IP warmup is not just about increasing email volume; it’s also about ensuring high-quality content and engagement. Here are some additional tips for a successful IP warmup:

Use Authentication Protocols

Implement email authentication methods such as SPF, DKIM, and DMARC. These protocols help verify that your emails are legitimate and not fraudulent, boosting your reputation with ISPs.


v=spf1 include:example.com -all

Regularly Clean Your Email List

Remove inactive or non-responsive subscribers from your email list to maintain a high engagement rate. High bounce rates or low engagement can adversely affect your IP reputation.


<!-- Pseudocode for List Cleaning -->

for subscriber in emailList:

  if subscriber.status == "inactive":


Monitor Metrics

Keep a close watch on email performance metrics such as open rates, click-through rates, bounce rates, and spam complaints. These insights can guide adjustments to your warmup strategy, ensuring better outcomes.

Benefits of IP Warmup

  • Improved Deliverability: Gradually increasing email volume helps avoid spam filters, leading to better inbox placement.
  • Boosted Sender Reputation: Consistent positive engagement during the warmup phase enhances your sender score and trustworthiness among ISPs.
  • Minimized Risk: IP warmup reduces the risk of being blacklisted by ISPs due to sudden large email sends.

In conclusion, IP warmup is an indispensable part of email marketing campaigns, especially when launching from a new IP address. By strategically controlling email volume, targeting engaged recipients, and maintaining high-quality content, marketers can establish a strong sender reputation, leading to improved email deliverability and overall campaign success.

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