What are best practices for IP warming strategy and email volume scaling?

Summary

IP warming is essential for new IP addresses to establish a positive sender reputation with ISPs. The core strategy involves gradually increasing email volume over several weeks, starting with a small, highly engaged segment of the audience. Different ESPs may offer varying recommendations, but a consistent approach is key. It's beneficial to distribute emails across a mix of domains. Monitor deliverability metrics (bounce rates, spam complaints) closely and adjust sending practices accordingly. Proper email authentication (SPF, DKIM, DMARC) is critical, as is maintaining a clean email list and sending high-quality, engaging content. Avoid sending spam or triggering spam traps. Leverage engagement data (opens, clicks, replies) to optimize the warming process. Gmail and Outlook.com have specific guidelines that should be followed. Overall, adapting the warming strategy based on feedback and engagement is crucial for success.

Key findings

  • Gradual Volume Increase: Gradually increase sending volume to build sender reputation.
  • Engagement is Key: Focus on sending to highly engaged subscribers initially.
  • Monitor Deliverability: Closely monitor deliverability metrics and adjust accordingly.
  • Authenticate Your Emails: Implement proper email authentication (SPF, DKIM, DMARC).
  • Maintain List Hygiene: Clean your email list to remove inactive/invalid addresses.
  • Avoid Spam Traps: Avoid sending spam or triggering spam traps.
  • Leverage Engagement Data: Use engagement data to optimize the warming process.
  • ESPs Vary: Different ESPs have varying IP warming recommendations.

Key considerations

  • Scaling Strategy: Determine a volume scaling strategy based on brand and IP factors (e.g., doubling volume weekly).
  • Domain Mix: Consider using a mix of domains (Gmail, Outlook, Yahoo) during the warming process.
  • ISP Guidelines: Familiarize yourself with specific guidelines from Gmail, Outlook.com, etc.
  • Feedback Adaptation: Adapt your strategy based on deliverability feedback (bounce rates, complaints).
  • Content Quality: Focus on sending high-quality, engaging content.

What email marketers say
10Marketer opinions

IP warming is a crucial process for establishing a positive sender reputation with ISPs when using a new IP address. The best practices involve gradually increasing email volume over several weeks, starting with a small, highly engaged segment of your audience. Maintaining a consistent sending volume and frequency is essential, avoiding sudden spikes or drops. Monitoring deliverability metrics like bounce rates and spam complaints is key to adjusting sending practices. Proper email authentication (SPF, DKIM, DMARC) is vital for verifying your sending identity. Cleaning your email list to remove inactive addresses and sending high-quality, engaging content are also recommended.

Key opinions

  • Gradual Volume Increase: Slowly increase sending volume over weeks to build reputation.
  • Engagement Focus: Prioritize sending to highly engaged subscribers initially.
  • Consistent Sending: Maintain consistent volume and frequency during warming.
  • Deliverability Monitoring: Closely track bounce rates, spam complaints, and deliverability metrics.
  • Authentication: Implement proper email authentication (SPF, DKIM, DMARC).
  • List Hygiene: Clean email lists to remove inactive or invalid addresses.
  • Engaging Content: Send high-quality content that encourages opens, clicks, and replies.

Key considerations

  • Segmented Sending: Segment your email lists and prioritize sending to your most engaged segments first.
  • Scaling Rate: Adjust the rate of volume increase based on deliverability feedback and engagement metrics.
  • ISP Guidelines: Familiarize yourself with the specific IP warming guidelines of major ISPs like Gmail and Outlook.
  • Blacklist Monitoring: Regularly check your IP address against blacklists to ensure you aren't being flagged as a spam source.
  • Reputation Monitoring: Continously monitor your sender reputation with tools like Google Postmaster Tools.
Marketer view

Email marketer from ActiveCampaign shares that it's essential to gradually increase sending volume over several weeks, starting with a small percentage of your list and slowly increasing it each day or week.

December 2021 - ActiveCampaign
Marketer view

Email marketer from Reddit user u/EmailExpert recommends starting with a very small send volume (e.g., a few hundred emails) and doubling it every few days, while closely monitoring bounce rates and spam complaints. Adjust the scaling rate based on the feedback you receive.

September 2022 - Reddit
Marketer view

Email marketer from HubSpot emphasizes focusing on sending to highly engaged subscribers during the initial stages of IP warming. This helps demonstrate positive engagement metrics to ISPs, improving deliverability.

December 2021 - HubSpot
Marketer view

Email marketer from SparkPost explains that segmenting your email lists and prioritizing sending to your most engaged segments during IP warming is crucial. This helps build a positive sender reputation quickly.

December 2024 - SparkPost
Marketer view

Email marketer from Litmus shares the importance of closely monitoring deliverability metrics (e.g., bounce rates, spam complaints) during IP warming. Adjust sending practices based on these metrics to ensure optimal deliverability.

October 2023 - Litmus
Marketer view

Email marketer from Mailgun explains that gradual IP warming is crucial. Start with a small volume of emails to engaged users, gradually increasing the volume over several weeks. This helps build a positive reputation with ISPs.

July 2024 - Mailgun
Marketer view

Email marketer from EmailOnAcid shares that proper email authentication (SPF, DKIM, DMARC) is essential during IP warming to verify your sending identity and improve deliverability.

August 2021 - EmailOnAcid
Marketer view

Email marketer from Mailjet highlights the importance of cleaning your email list before and during IP warming to remove inactive or invalid email addresses. This helps reduce bounce rates and improve your sender reputation.

October 2022 - Mailjet
Marketer view

Email marketer from SendGrid shares the importance of maintaining a consistent sending volume and frequency during IP warming. Avoid sudden spikes or drops in volume, as this can negatively impact your sender reputation.

February 2025 - SendGrid
Marketer view

Email marketer from StackOverflow user EmailGuru emphasizes the importance of sending high-quality, engaging content during IP warming. Content that generates opens, clicks, and replies will improve your sender reputation and deliverability.

February 2024 - StackOverflow

What the experts say
6Expert opinions

IP warming is the process of gradually increasing email volume from a new IP address to build a positive sender reputation with ISPs. Approaches vary across ESPs, but generally, it involves starting with a small, highly engaged audience segment. Volume can be scaled daily or weekly, adjusting the rate based on factors like brand, IPs, and email type. A common strategy is doubling the send volume each week. It's also beneficial to distribute emails across a mix of domains (Gmail, Outlook, Yahoo, etc.). Crucially, avoid sending spam or triggering spam traps to prevent blacklisting. Monitoring sender reputation, leveraging engagement data (opens, clicks, replies), and maintaining list hygiene are essential for successful IP warming.

Key opinions

  • Gradual Volume Increase: Gradually increase email volume to build a positive reputation.
  • ESPs Vary: Different ESPs may have varying IP warming recommendations.
  • Mix of Domains: Distribute emails across a mix of domains during IP warming.
  • Engagement Data: Leverage engagement data (opens, clicks, replies) to improve reputation.
  • Avoid Spam: Avoid sending spam or triggering spam traps.

Key considerations

  • Volume Scaling Strategy: Determine a volume scaling strategy, such as doubling volume weekly or increasing daily.
  • Brand and IP Factors: Adjust volume scaling based on factors like brand, number of IPs, and email type.
  • Reputation Monitoring: Monitor sender reputation to identify and address any issues promptly.
  • List Hygiene: Maintain a clean email list to avoid sending to inactive or invalid addresses.
Expert view

Expert from Spam Resource explains that IP warming involves gradually increasing the volume of emails sent from a new IP address to establish a positive reputation with ISPs. They recommend starting with a small, highly engaged segment of your audience and slowly increasing the volume over time.

August 2021 - Spam Resource
Expert view

Expert from Email Geeks suggests using a mix of domains during IP warming. Provides an example of how 7,000 emails could be distributed across Gmail, Outlook, Yahoo, Comcast, and other domains.

April 2024 - Email Geeks
Expert view

Expert from Email Geeks suggests doubling email sends week over week during IP warming. Starting with 1% of the list in week one, then 2% in week two, 4% in week three, and so on until the entire list is reached in a week.

August 2023 - Email Geeks
Expert view

Expert from Spam Resource shares that during IP warming, it's crucial to avoid sending spam or triggering spam traps, as this can lead to blacklisting. They advise carefully monitoring your sender reputation and addressing any issues promptly.

August 2023 - Spam Resource
Expert view

Expert Laura Atkins from Word to the Wise shares that leveraging engagement data (opens, clicks, replies) during IP warming is essential. Sending to engaged subscribers helps build a positive reputation and improves deliverability. They also stress the importance of list hygiene.

December 2023 - Word to the Wise
Expert view

Expert from Email Geeks shares that different ESPs have varying IP warming recommendations, including rate limiting and gradual IP shifting. Matt typically starts with volume-based sending, increasing recipients daily, with the specific numbers depending on factors like brand, number of IPs, and mail type.

January 2025 - Email Geeks

What the documentation says
3Technical articles

Both Gmail and Outlook.com recommend a warming-up period for new IP addresses. This involves gradually increasing sending volume based on user engagement. RFC standards emphasize adhering to best practices for email sending, including proper authentication and avoiding spam-like behavior, all of which are relevant to successful IP warming. Monitoring sender reputation and adjusting volume accordingly is also recommended.

Key findings

  • Gradual Ramp-Up: Both Gmail and Outlook.com recommend a gradual ramp-up of sending volume for new IPs.
  • User Engagement: Google recommends increasing volume based on user engagement.
  • Reputation Monitoring: Microsoft recommends monitoring sender reputation and adjusting volume accordingly.
  • RFC Standards: RFC standards emphasize adherence to email best practices.

Key considerations

  • Gmail Guidelines: Review Gmail's bulk sender guidelines for specific recommendations.
  • Outlook.com Policies: Adhere to Outlook.com's sender policies and best practices.
  • SMTP Compliance: Ensure your email setup complies with SMTP standards to avoid deliverability issues.
  • Authentication: Implement proper email authentication (SPF, DKIM, DMARC) as per RFC recommendations.
Technical article

Documentation from Gmail Help explains that new IP addresses sending mail to Gmail should follow a warming-up period. Google recommends starting with a low volume and gradually increasing it based on user engagement.

March 2022 - Gmail Help
Technical article

Documentation from RFC details the standards for SMTP, emphasizing the importance of adhering to established best practices for email sending, including proper authentication and avoiding spam-like behavior, which are relevant during IP warming.

September 2021 - RFC-Editor
Technical article

Documentation from Microsoft outlines sender best practices for Outlook.com, suggesting a gradual ramp-up of sending volume for new IPs. They recommend monitoring sender reputation and adjusting volume accordingly.

June 2023 - Microsoft