Summary
When transitioning email sending from a primary domain to a subdomain, a multi-faceted approach is essential for maintaining deliverability. This includes technical configurations, reputation building, and content optimization. Core technical steps are updating SPF, DKIM, and DMARC records to authenticate the new subdomain, verifying reverse DNS records, and configuring the subdomain within the email sending platform. Simultaneously, building a positive reputation involves warming up the subdomain by gradually increasing sending volume, and possibly using a second DKIM signature for accelerated learning by mailbox providers. Proactive reputation monitoring using tools like Google Postmaster Tools is critical. Segmenting email streams onto distinct subdomains (if appropriate) to maintain deliverability by isolating any email type is also a consideration. Further, maintain good list hygiene, optimize email content to avoid spam triggers, test rendering, encourage subscriber engagement, and establish feedback loops with email providers.
Key findings
- DNS Authentication: Update SPF, DKIM, and DMARC records for the subdomain.
- Reputation Building: Warmup the subdomain gradually and monitor its reputation.
- Subdomain Configuration: Properly configure the subdomain within your email sending platform.
- Email Stream Separation: Consider using separate subdomains for different email streams.
- List Hygiene: Maintain a clean email list for deliverability.
- Content Optimization: Optimize email content to avoid spam triggers.
- DKIM Signing Order: DKIM signing order can influence sender reputation.
- IP Warmup: If the IP changes, implement a proper IP warmup strategy.
- PTR Record: Verify the reverse DNS record is properly configured.
- HELO domain Considerations: Appropriate decision about HELO domain may be needed.
Key considerations
- Phased Implementation: Implement changes in phases to monitor deliverability impact.
- Proactive Monitoring: Continuously monitor sender reputation using available tools.
- Sender Platform Settings: Ensure subdomain settings and authentication are accurate on your sending platform.
- Content Scrutiny: Regularly review email content for spam triggers and best practices.
- List Management: Implement strategies for list cleaning and validation.
- Feedback Loops: Set up feedback loops to monitor spam complaints.
- Authentication Verification: Validate SPF, DKIM, and DMARC records using a checker.
- Adaptability: Be prepared to adapt strategies based on monitoring and feedback.
- HELO Domain: Assess whether the HELO domain should be changed or kept the same.
What email marketers say
10 marketer opinions
When switching from a primary domain to a subdomain for email sending, a comprehensive checklist should be followed to maintain or improve deliverability. Key areas include warming up the new subdomain by gradually increasing email volume, diligently monitoring sender reputation metrics (bounce rates, spam complaints), and ensuring proper configuration of DNS records (SPF, DKIM, DMARC). Implementing IP warmup if the IP address is also changing, setting up feedback loops with major email providers, maintaining good email list hygiene, optimizing email content, and testing email rendering across various platforms are also crucial. Furthermore, engaging subscribers through relevant content and clear calls-to-action is essential for long-term deliverability success. Separating email streams by subdomain, if applicable, helps maintain sender reputation by isolating potential deliverability problems.
Key opinions
- Subdomain Warmup: Gradually increase email volume to establish a positive reputation.
- Reputation Monitoring: Continuously monitor sender reputation and deliverability metrics.
- DNS Configuration: Verify SPF, DKIM, and DMARC records for the subdomain.
- IP Warmup (if applicable): Implement IP warmup alongside subdomain warmup when changing IPs.
- Feedback Loops: Set up feedback loops with major email providers to monitor spam complaints.
- List Hygiene: Maintain good email list hygiene by removing inactive subscribers.
- Content Optimization: Optimize email content to avoid spam triggers.
- Email Testing: Test email rendering across different email clients.
- Subscriber Engagement: Focus on engaging subscribers with relevant content.
- Subdomain Separation: Consider using separate subdomains for different email streams to help prevent deliverability problems.
Key considerations
- Gradual Warmup: Avoid sudden spikes in sending volume to prevent deliverability issues.
- Proactive Monitoring: Regularly monitor sender reputation and take prompt action to address problems.
- Authentication: Ensure SPF, DKIM, and DMARC are correctly configured to authenticate emails.
- Email Content: Pay close attention to email content and structure to prevent spam classification.
- List Maintenance: Regularly clean your email list to improve engagement and reduce bounce rates.
- Test and Validate: Thoroughly test and validate configurations before fully transitioning to the subdomain.
- Segment Streams: Segment email streams onto different subdomains based on email type for maintainability.
Marketer view
Email marketer from Litmus says to use a DNS record checker to verify that your SPF, DKIM, and DMARC records are correctly configured for the subdomain. This ensures that your email authentication settings are properly implemented and can help prevent deliverability issues.
11 Jun 2024 - Litmus
Marketer view
Email marketer from Email Geeks says it's a good idea to make it obvious what the stream is for by using separate subdomains.
20 Apr 2023 - Email Geeks
What the experts say
5 expert opinions
When transitioning email sending from a primary domain to a subdomain, several factors are critical for maintaining deliverability. Warming up the subdomain is essential, which can be accelerated by using a secondary DKIM signature to introduce the new domain to machine learning filters. Separating subdomains for different email types might be beneficial depending on volume and deliverability risks. It's crucial to properly configure the subdomain within the email sending platform, ensuring all authentication settings are in place. DKIM signing order matters, influencing how ISPs assess reputation. Finally, different approaches to subdomain setup might be needed based on specific scenarios, including decisions about changing the HELO domain.
Key opinions
- Subdomain Warmup: Warming up the subdomain is essential for positive reputation with mailbox providers.
- Secondary DKIM Signature: Adding a secondary DKIM signature can accelerate the subdomain warmup process.
- Subdomain Separation: Separate subdomains are useful for different email streams but not always necessary.
- Proper Configuration: Ensuring the subdomain is correctly configured within the email sending platform is crucial.
- DKIM Signing Order: DKIM signing order impacts how ISPs assess reputation.
- HELO Domain Considerations: Different HELO domain approaches may be necessary for influencing sender reputation based on the situation.
Key considerations
- Warmup Strategy: Determine the appropriate warmup strategy, considering using a secondary DKIM signature.
- Volume and Deliverability: Assess email volume and deliverability concerns when deciding to separate subdomains.
- Platform Configuration: Ensure all necessary authentication settings are in place within the email sending platform.
- Signing Order: Strategically manage the DKIM signing order to optimize reputation benefits.
- HELO Settings: Assess whether the HELO domain should be changed or kept the same, as it influences sending reputation.
Expert view
Expert from Spam Resource explains that when switching to a subdomain, it is crucial to ensure that the subdomain is properly configured within your email sending platform. Verify that the subdomain is correctly set up for sending emails and that all necessary configurations, such as authentication settings, are in place. Check that your email sending platform recognizes the new subdomain and can send emails on its behalf.
3 Oct 2021 - Spam Resource
Expert view
Expert from Email Geeks explains DKIM signing order. In header order (top down as reading headers): known signature then new signature. In signing order (so as you sign the outbound message): new signature than known signature. After a while you can switch them so it’s (header order) new signature then known signature. Then you can drop the old signature.
18 May 2025 - Email Geeks
What the documentation says
4 technical articles
When transitioning email sending from a primary domain to a subdomain, it is essential to update DNS records to ensure proper authentication and deliverability. This includes updating SPF records to authorize the subdomain's sending sources, generating and publishing a new DKIM record for the subdomain to sign emails correctly, updating the DMARC record to align with sending practices, and verifying that the reverse DNS (PTR) record is properly configured and matches the hostname of the sending server.
Key findings
- SPF Record Update: SPF records must be updated to include the subdomain as an authorized sending source.
- DKIM Record Generation: A new DKIM record should be generated and published for the subdomain.
- DMARC Record Update: DMARC record needs to be updated to include the subdomain, ensuring policy alignment.
- Reverse DNS (PTR) Record Verification: Verify the reverse DNS record is properly configured and matches the sending server's hostname.
Key considerations
- Accurate SPF Configuration: Ensure the SPF record accurately reflects all sending sources for the subdomain.
- DKIM Key Validation: Validate the DKIM configuration to confirm emails are signed correctly.
- DMARC Policy Alignment: Ensure the DMARC policy aligns with sending practices for the subdomain.
- Hostname Matching: Confirm that the PTR record matches the sending server's hostname to establish trust.
Technical article
Documentation from Google Workspace Admin Help explains that you need to update your SPF records to include the subdomain. This involves adding the subdomain to the existing SPF record or creating a new SPF record specifically for the subdomain. Ensure the SPF record accurately reflects the sending sources for the subdomain to avoid deliverability issues. The URL provided explains more on using SPF records.
6 Sep 2024 - Google Workspace Admin Help
Technical article
Documentation from RFC standard explains that verify that your reverse DNS (PTR) record is properly configured for the sending IP address. The PTR record should match the hostname of your sending server, helping to establish trust with email receivers. More information on reverse DNS can be found via the link.
20 Dec 2022 - RFC-Editor
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