Summary
Experts and marketers overwhelmingly advise against using a new subdomain to warm up old contacts. Warming a subdomain requires sending to engaged users to build a positive reputation. Sending to cold, unengaged contacts can negatively impact the subdomain's reputation from the outset. Instead, it’s recommended to clean and segment your existing email list, implement re-engagement campaigns, verify email addresses, use a gradual approach to increasing send volume, authenticate your emails, and monitor your sender reputation.
Key findings
- Subdomain Warm-up: New subdomains should be warmed with engaged users, not cold contacts, to establish a positive sending reputation.
- List Segmentation: Proper list segmentation based on engagement, demographics, and purchase history is crucial before sending to old contacts.
- List Cleaning: Cleaning your email list by removing inactive subscribers, hard bounces, and unsubscribes is essential for improving sender reputation.
- Re-engagement: Re-engagement campaigns can help warm up old contacts and identify active users.
- Email Authentication: SPF, DKIM, and DMARC are critical for authenticating emails and improving deliverability.
- Gradual Volume Increase: Avoid sending high-volume emails to cold leads at once; gradually increase volume over time.
- Verify Email Addresses: Verify email addresses to avoid sending to non-existent or spam trap addresses.
Key considerations
- Sender Reputation: Poor sending practices can negatively impact your overall email deliverability and sender reputation.
- Monitoring: Monitor engagement metrics, bounce rates, and sender reputation to identify and address deliverability issues.
- Tool Utilization: Consider using third-party tools to identify engaged emails, verify addresses, and manage email cadence.
- Authentication: Properly implement and maintain SPF, DKIM, and DMARC for optimal email authentication.
- Compliance: Adhere to email marketing regulations and provide clear opt-out options to avoid being flagged as spam.
What email marketers say
10 marketer opinions
The consensus among email deliverability experts is that using a new subdomain to warm up old contacts is generally not recommended. Warming a subdomain requires sending to engaged users to build a positive reputation. Sending to old, unengaged contacts can negatively impact the subdomain's reputation from the start. Instead, it's advised to focus on cleaning and segmenting your existing email list, implementing re-engagement campaigns, and using a gradual approach to warming up contacts with a good email cadence tool.
Key opinions
- Subdomain Warm-up: New subdomains need to be warmed up with engaged users, not cold contacts, to build a positive sending reputation.
- List Segmentation: Proper list segmentation based on engagement, demographics, and purchase history is crucial for deliverability when dealing with old contacts.
- List Cleaning: Cleaning your email list by removing inactive subscribers, hard bounces, and unsubscribes is essential to improve sender reputation.
- Re-engagement Campaigns: Implementing re-engagement campaigns with value and incentives can help warm up old contacts and identify active users.
- Gradual Approach: Avoid sending high-volume emails to cold leads at once; use a steady approach with gradual volume increases and a good email cadence tool.
Key considerations
- Deliverability Impact: Poor sending practices to old contacts can negatively impact your overall email deliverability and sender reputation.
- Engagement Metrics: Monitor engagement metrics such as open rates, click-through rates, and response rates to gauge the effectiveness of your warm-up efforts.
- Authentication: Ensure your emails are properly authenticated using SPF, DKIM, and DMARC to improve deliverability and avoid being flagged as spam.
- Third-Party Tools: Consider using third-party tools to identify engaged emails or verify the validity of old email addresses.
- Compliance: Always comply with email marketing regulations and respect user preferences by providing clear opt-out options.
Marketer view
Marketer from Email Geeks advises against creating a new subdomain for mail expected to perform poorly, as new subdomains require warming. Suggests folding the data into higher-performing traffic or not sending to them at all if there is a worry of risk to deliverability.
15 Feb 2024 - Email Geeks
Marketer view
Email marketer from Reddit shares to segment your old contacts based on how old they are. Start by sending to the most recent ones first, and gradually work your way back. Also, clean your list by removing hard bounces and unsubscribes before starting your warm-up campaign.
10 Mar 2025 - Reddit
What the experts say
3 expert opinions
Experts in email deliverability recommend against using old contacts for warming up a new IP address or domain. They emphasize the importance of verifying the validity of old email addresses, sending to engaged subscribers to establish a positive sender reputation, ensuring the list is legitimate, and authenticating your emails. These practices help demonstrate to email providers that you are a responsible sender with permission from your recipients.
Key opinions
- Verify Email Addresses: Before sending any emails, especially to old contacts, verify their validity to avoid sending to non-existent or spam trap addresses.
- Engaged Subscribers for Warming: Use only your best and most engaged subscribers for warming up a new IP or domain, not old or unengaged contacts.
- List Legitimacy: Ensure your email list contains real people and does not include spam traps or other illegitimate addresses.
- Authentication is Key: Properly authenticate your emails to demonstrate to email providers that you are a legitimate sender.
Key considerations
- Sender Reputation: Building a good sender reputation is crucial for email deliverability, and starting with engaged subscribers is essential for a positive start.
- Email Verification Tools: Consider using tools like Kickbox to verify the validity of old email addresses before including them in any sending campaigns.
- Legitimate Sending Practices: Adhering to legitimate sending practices and avoiding spam traps are vital for maintaining a good sender reputation.
- Email Authentication: Implement SPF, DKIM, and DMARC to authenticate your emails and improve deliverability.
Expert view
Expert from Word to the Wise explains that when warming an IP or Domain you are showing email providers that you are a good sender and that you have permission with your recipients. It is important to send to your best subscribers when warming, instead of old contacts. It is also key to authenticate your email.
29 May 2022 - Word to the Wise
Expert view
Expert from Email Geeks recommends checking with a user or using Kickbox to verify old email addresses, as some may no longer exist.
20 Sep 2024 - Email Geeks
What the documentation says
5 technical articles
Email deliverability documentation emphasizes authentication using SPF, DKIM, and DMARC to verify sender legitimacy and prevent spoofing. Monitoring sender reputation and NDRs (bounce messages) are essential for identifying and addressing deliverability issues. Following these practices helps ensure emails reach their intended recipients and avoid being flagged as spam.
Key findings
- Email Authentication: SPF, DKIM, and DMARC are crucial for authenticating emails and preventing spoofing, which significantly improves deliverability.
- Sender Reputation: Monitoring sender reputation helps identify potential issues and ensure emails are not being flagged as spam.
- NDR Monitoring: Monitoring Non-Delivery Reports (NDRs) or bounce messages is important for identifying undeliverable emails and potential spam issues.
- Policy Enforcement: DMARC provides a policy for handling emails that fail SPF and DKIM authentication, protecting against spoofing and phishing attacks.
Key considerations
- Implementation: Properly implementing SPF, DKIM, and DMARC requires technical expertise and careful configuration of DNS records.
- Ongoing Monitoring: Regularly monitor sender reputation and NDRs to proactively identify and address deliverability issues.
- Policy Enforcement: Establish a clear DMARC policy to specify how receiving mail servers should handle unauthenticated emails.
- Best Practices: Adhering to email deliverability best practices, as outlined by Google Postmaster Tools, is crucial for maintaining a good sending reputation.
Technical article
Documentation from DKIM explains signing your emails with a DKIM signature to verify their authenticity. DKIM helps receiving mail servers verify that the content of your emails hasn't been tampered with during transit.
8 Jun 2025 - DKIM
Technical article
Documentation from Google Postmaster Tools explains how to improve your email deliverability by following their best practices. Authenticate your emails using SPF, DKIM, and DMARC, and monitor your sender reputation to ensure you're not being flagged as spam. This can help you to avoid issues.
14 Mar 2023 - Google Postmaster Tools
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