Summary
Warming up an old email list requires a comprehensive strategy encompassing list hygiene, gradual engagement, technical setup, and constant monitoring. Experts recommend defining 'old' based on mailing frequency and then focusing on those who have recently engaged with your emails. You must suppress unengaged addresses, and cleaning the list with services is crucial. Key technical aspects involve email authentication (SPF, DKIM, DMARC), monitoring sender reputation and blacklists, and adhering to SMTP standards. Gradually increasing the volume of emails sent, and sending targeted re-engagement campaigns with incentives are recommended. Setting clear expectations in initial emails and monitoring key engagement metrics like open rates are also important. Experts also suggest not sending email from your corporate domain. Running deliverability tests and checking for spam traps before the warm-up are essential.
Key findings
- List Hygiene: Cleaning the list by removing invalid addresses, spam traps, and unengaged subscribers is critical for improving deliverability.
- Gradual Engagement: Gradually increasing email volume avoids triggering spam filters and allows for controlled testing and adjustment.
- Technical Setup: Proper email authentication (SPF, DKIM, DMARC) and adherence to SMTP standards are fundamental for deliverability.
- Re-engagement is Key: Sending re-engagement emails to people who want the mail gives you the best chance of warming up the list.
- Monitoring: Continuous monitoring of sender reputation, blacklists, and engagement metrics is necessary to identify and address deliverability issues.
- Importance of Segmentation: Segmenting your email list based on subscribers who have engaged with the emails.
- Attrition: Email lists decay over time, approximately 30% per year.
Key considerations
- Defining 'Old': Determine whether the list is defined as old based on length since the list was built or if the list has been actively mailed too.
- Opt-In Clarity: Clearly remind recipients how they joined the list and provide easy opt-out options.
- Testing: Make sure to test the list for issues before mailing. Blacklists, spam traps, etc.
- Authentication: Set up authentication for the domain that is going to be mailing the old list.
- Compliance with Standards: Ensure adherence to SMTP standards for optimal delivery.
- Sending Reputation: Address bounces and bad emails quickly or this will effect your sending reputation.
- Is it worth the risk?: Consider the risk mailing an old list, could cause more damage than it's worth.
What email marketers say
10 marketer opinions
Warming up an old email list requires a multi-faceted approach focusing on list hygiene, gradual engagement, and monitoring. Experts recommend segmenting the list based on engagement, removing invalid addresses and unengaged subscribers, and avoiding spam traps. Gradual sending, re-engagement campaigns with incentives, and setting clear expectations in initial emails are crucial. Using a non-corporate sending domain, and consistently monitoring engagement metrics like open rates and unsubscribes are also recommended.
Key opinions
- List Hygiene: Cleaning the list by removing invalid addresses, spam traps and unengaged subscribers is critical for improving deliverability and sender reputation.
- Gradual Engagement: Gradually increasing the volume of emails sent over time, starting with a small batch, helps avoid triggering spam filters.
- Re-engagement Campaigns: Sending targeted re-engagement campaigns with incentives encourages subscribers to re-subscribe or update their preferences.
- Set Expectations: Set clear expectations in initial emails, reminding subscribers why they are receiving the email and providing an easy way to unsubscribe.
- Monitor Metrics: Consistently monitor engagement metrics such as open rates, click-through rates, and unsubscribe rates to optimize your campaigns.
Key considerations
- Sending Domain: Consider using a sending domain separate from your corporate domain to protect your primary domain's reputation.
- Welcome Series: Implement a welcome series for new subscribers to ensure they are legitimate and actively engaging with your emails.
- Compliance: Always provide a clear and easy way for subscribers to unsubscribe to comply with anti-spam regulations.
- Spam Traps: Take steps to avoid landing in spam traps when using old lists.
- Segment Sending: Segmented sending allows you to send emails to people who actively want the emails and improve your email sender reputation.
Marketer view
Email marketer from Email Geeks suggests checking into which domains you are sending from and that you should not use the corporate domain for sending to your lists
16 Jun 2022 - Email Geeks
Marketer view
Email marketer from Reddit recommends gradually increasing the volume of emails sent to your list over time. Start with a small batch and gradually increase the number of emails sent each day to avoid triggering spam filters.
17 May 2025 - Reddit
What the experts say
5 expert opinions
Warming up an old email list presents unique challenges due to address attrition and potential deliverability issues. Experts emphasize the importance of defining 'old' based on mailing frequency, suppressing inactive addresses, and focusing on recently engaged subscribers. Cleaning the list with services like Kickbox and providing clear opt-out options in initial emails are vital to avoid spam complaints and maintain a positive sending reputation.
Key opinions
- Address Attrition: Email addresses degrade over time, with a significant percentage becoming invalid each year, impacting deliverability.
- Definition of 'Old': The term 'old' depends on mailing frequency; a list never mailed is 'old' regardless of collection date, and lists mailed daily are not.
- Suppression is Key: Suppressing unengaged or potentially invalid addresses is crucial for protecting sender reputation.
- Focus on Engaged Subscribers: Warming up efforts should prioritize subscribers who have recently interacted with your emails.
- Cleaning Tools: Using email verification services helps identify and remove invalid addresses before sending.
Key considerations
- Opt-Out Clarity: Clearly state how recipients provided their email address and offer a simple opt-out option to minimize spam complaints.
- Sending Reputation: Bounces from undeliverable addresses negatively impact sender reputation; proactively manage list quality.
- Relevance is Critical: Ensure emails are relevant to recipients who haven't been contacted in a while to increase engagement.
- Consent: Mailing to only people who have asked for mail is more important.
- Risk Assessment: Know the older the list the more risky sending to it is.
Expert view
Expert from Email Geeks shares that attrition rates on email addresses over time are high, with approximately 30% of addresses becoming invalid within a year.
7 Sep 2022 - Email Geeks
Expert view
Expert from Email Geeks suggests using a service like Kickbox to clean the email list. They also recommend including a clear reminder in the initial emails about how the recipient provided their email address, along with an easily accessible opt-out link, to encourage unsubscribes rather than spam complaints.
20 Apr 2025 - Email Geeks
What the documentation says
5 technical articles
Warming up an old email list requires careful attention to technical details to ensure deliverability. Documentation emphasizes the importance of email authentication (SPF, DKIM, DMARC), monitoring sender reputation and blacklists, adhering to SMTP standards, and running deliverability tests before starting the warm-up process. Addressing these technical aspects helps improve deliverability and avoid damaging your sender reputation.
Key findings
- Email Authentication: Implementing SPF, DKIM, and DMARC is crucial for proving your identity and improving deliverability, especially to Gmail inboxes.
- Sender Reputation: Monitoring your sender reputation and IP address for blacklisting is essential for identifying and resolving deliverability issues.
- SMTP Standards: Adhering to SMTP standards (RFC 5321) ensures proper email formatting and delivery.
- Deliverability Testing: Running deliverability tests helps identify potential issues before they impact your sender reputation.
- Blacklist Checks: Checking if your IP address or domain is on any major blacklists is important to avoid deliverability problems.
Key considerations
- Technical Expertise: Implementing email authentication and monitoring sender reputation may require technical expertise or the use of specialized tools.
- Proactive Monitoring: Regularly monitor your sender reputation and blacklist status to detect and address issues promptly.
- Standard Compliance: Ensure your email formatting and sending practices comply with SMTP standards.
- Test Environment: Use a testing environment to run deliverability tests without impacting your production sending.
- Remediation: Develop a plan for addressing any issues identified during deliverability testing or blacklist monitoring.
Technical article
Documentation from Microsoft stresses the importance of monitoring your sender reputation and IP address for blacklisting. Use tools like Microsoft SNDS (Smart Network Data Services) to track your reputation and resolve any issues.
18 May 2022 - Microsoft
Technical article
Documentation from RFC outlines the importance of adhering to SMTP standards (RFC 5321) to ensure proper email formatting and delivery. This includes using valid headers, HELO/EHLO greetings, and message formatting.
23 Nov 2024 - RFC Editor
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