Summary
Warming up a new subdomain for email sending involves gradually increasing email volume, beginning with highly engaged users and transactional emails to establish a positive sending reputation. Proper email authentication (SPF, DKIM, and DMARC) is critical, with DKIM alignment playing a key role in DMARC compliance. Relaxed alignment (subdomain relationship) is generally acceptable, while strict alignment may be required by DMARC policies. Consistent sending practices, high-quality content, and active monitoring of deliverability metrics are crucial. Addressing existing deliverability issues and avoiding spam traps further enhance the success of subdomain warming. Testing and checking authentication can also help boost your chances of success.
Key findings
- Gradual Volume Increase: Gradually increase email volume to build a positive sending reputation.
- Email Authentication (SPF, DKIM, DMARC): Proper configuration of SPF, DKIM, and DMARC records is essential for subdomain setup and authentication.
- DKIM Alignment: DKIM alignment (strict or relaxed) impacts DMARC policies; relaxed alignment is generally acceptable with subdomains, but strict alignment may be required.
- Content Quality and Engagement: Sending high-quality content that generates engagement is crucial for a positive sender reputation.
- Reputation Inheritance: Subdomains inherit some reputation from the parent domain but require establishing their own.
- Testing: Testing for proper authentication is important.
Key considerations
- Monitoring Metrics: Actively monitor deliverability metrics (open rates, click-through rates, spam complaints) to identify and address issues.
- Pre-existing Deliverability Issues: Resolve any existing deliverability problems before migrating to a new subdomain.
- MS Preemptive Accommodation: Consider submitting a ticket for MS preemptive accommodation (especially for new IPs).
- Spam Traps: Implement list management practices to avoid spam traps.
- Email Header Analysis: Inspect Email Headers to make sure Authentication is valid.
- Consistent Sending Practices: Adopt Consistent Sending Practices from Google.
What email marketers say
11 marketer opinions
Warming up a new subdomain for email sending involves gradually increasing email volume, starting with engaged users and transactional emails to build a positive sending reputation. Proper email authentication (SPF, DKIM, DMARC) is crucial, with DKIM alignment playing a key role in DMARC compliance. Monitoring deliverability metrics, managing content quality, and avoiding existing deliverability issues are essential for successful subdomain warmup.
Key opinions
- Gradual Volume Increase: Gradually increase email volume, starting with engaged users, to build a positive sending reputation.
- Email Authentication: Ensure proper SPF, DKIM, and DMARC configuration for the subdomain.
- DKIM Alignment: Align DKIM signatures with the 'From' domain to ensure DMARC compliance; relaxed alignment (subdomain relationship) is generally acceptable, but strict alignment may be required by DMARC policies.
- Content Quality: Send high-quality content that recipients want to engage with to signal a positive sender reputation.
- Reputation Inheritance: Subdomains inherit some reputation from the parent domain but need to establish their own.
- Test and Confirm Reputation: Confirm reputation by sending a low volume of test messages over a period of days or weeks.
Key considerations
- Monitoring Metrics: Monitor deliverability metrics like open rates, click-through rates, bounce rates, and spam complaints to identify and address issues promptly.
- Existing Issues: Resolve any existing deliverability issues before moving to a new subdomain.
- MS Preemptive Accommodation: Consider submitting a ticket for MS preemptive accommodation, especially if using a new IP address.
- Authentication Basics: Test to confirm that your authentication is working you can check the headers on the email.
- Subscriber Engagement: Target engaged subscribers initially to establish a strong sending reputation.
Marketer view
Marketer from Email Geeks shares that MS preemptive accommodation is mainly for new IPs, suggesting submitting a ticket for the subdomain with the understanding it might have no effect. He emphasizes that warmups heavily depend on content and audience, requiring introduction of the mail stream to message filters to avoid being seen as a complaint generator. He highlights the importance of content and audience. Also notes that general advice becomes less useful as specifics of volumes and mail program increase.
9 Dec 2024 - Email Geeks
Marketer view
Email marketer from Reddit explains that starting with highly engaged subscribers on a new subdomain is a good practice. This helps establish a positive sending reputation quickly. Monitor feedback loops and address any deliverability issues promptly.
12 Aug 2021 - Reddit
What the experts say
2 expert opinions
When warming up a new subdomain, establishing a positive reputation involves sending a low volume of test messages over days or weeks to confirm reputation. Verifying that email authentication is working can be done by examining email headers.
Key opinions
- Confirm Reputation: Send a low volume of test messages over a period of days or weeks to confirm a positive reputation.
- Check Authentication: Verify that email authentication is working by checking email headers.
Key considerations
- Testing Volume: Ensure the test volume is low enough to avoid negatively impacting deliverability.
- Header Analysis: Understand how to interpret email headers to confirm proper authentication.
Expert view
Expert from Word to the Wise answers explains that to check that your authentication is working you can check the headers on the email.
10 Jun 2023 - Word to the Wise
Expert view
Expert from Spamresource explains that establishing a positive reputation can be achieved by sending a low volume of test messages over a period of days or weeks to confirm reputation.
24 Mar 2025 - Spamresource
What the documentation says
4 technical articles
Properly configuring SPF, DKIM, and DMARC records is essential for authenticating email sending from a new subdomain. DKIM alignment, which can be strict or relaxed, affects how DMARC policies are applied. Consistent sending practices, alongside correct authentication, are vital for maintaining good deliverability and preventing emails from being marked as spam. Subdomain warming involves gradually increasing email volume and monitoring sender reputation.
Key findings
- Authentication Importance: Correct SPF, DKIM, and DMARC configuration is vital for subdomain setup.
- DKIM Alignment Modes: DKIM alignment modes (strict and relaxed) impact how DMARC policies are applied.
- DMARC Dependence: DMARC relies on DKIM and SPF for email authentication and requires alignment with the 'From' header domain.
- Holistic Approach: Consistent sending practices and email authentication are vital for maintaining good deliverability.
Key considerations
- Record Accuracy: Ensure SPF, DKIM, and DMARC records are accurately configured for the subdomain.
- Alignment Choice: Understand and choose the appropriate DKIM alignment mode based on DMARC policies.
- Reputation Monitoring: Monitor sender reputation as part of the subdomain warmup process.
Technical article
Documentation from Microsoft shares guidelines that consistent sending practices and proper email authentication (SPF, DKIM, DMARC) are vital for maintaining good deliverability. Warming up a subdomain involves gradually increasing email volume and monitoring sender reputation.
28 Feb 2024 - Microsoft
Technical article
Documentation from Google explains that when setting up a subdomain, ensure that SPF, DKIM, and DMARC records are correctly configured for the subdomain to authenticate email sending. Proper authentication helps establish trust with mailbox providers and prevents emails from being marked as spam.
19 Nov 2024 - Google
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