Summary
The use of subdomains in email marketing significantly impacts deliverability primarily through enhanced control over sender reputation and authentication. While there's no specific deliverability benefit to using sub-subdomains over subdomains, the strategic segmentation of email traffic—such as separating marketing and transactional emails onto distinct subdomains—allows for better isolation of reputation issues, protecting the main domain's overall deliverability. Proper implementation of SPF, DKIM, and DMARC on each subdomain is critical, as is the practice of 'warming up' new subdomains to gradually build a positive sender reputation. Each subdomain's reputation must be managed independently, and different subdomains may require different SPF configurations. Effective subdomain strategies enhance deliverability by providing granular control, enabling the differentiation of sending streams, and facilitating DMARC alignment.
Key findings
- Segmentation Protects Reputation: Segmenting email traffic by type onto separate subdomains allows for better isolation of reputation issues, protecting the main domain's deliverability.
- Authentication is Essential: Proper setup of SPF, DKIM, and DMARC on each subdomain is crucial for authentication and improved deliverability.
- Warming Up is Critical: Gradually warming up new subdomains helps establish a positive sender reputation.
- Reputation Management: Each subdomain's reputation should be managed independently to prevent one affecting others.
- No Deliverability Benefit Sub Vs Sub-Sub: Deliverability is not directly improved from using Sub vs Sub-Sub domains. These are mainly used for tracking purposes.
Key considerations
- Organizational Benefits: Consider using subdomains to organize different types of email traffic or to assign to specific ESPs.
- Monitor Subdomain Reputation: Actively monitor the reputation of each subdomain to identify and address deliverability issues promptly.
- Authentication Settings: Ensure correct and consistent SPF, DKIM, and DMARC settings across all subdomains.
- Warming Strategy: Implement a structured subdomain warmup strategy to slowly build a good reputation.
- SPF Configuration: Configure SPF records based on the specific requirements of each subdomain's sending stream and `MAIL FROM` address.
What email marketers say
9 marketer opinions
Using subdomains and sub-subdomains in email marketing has a nuanced impact on deliverability. While deliverability may not differ significantly between subdomains and sub-subdomains, the primary benefit lies in organization, reputation management, and segmentation. Segmenting email traffic by type (e.g., marketing vs. transactional) onto separate (sub)domains allows for better isolation of reputation issues and improved overall deliverability. Proper setup of authentication protocols (SPF, DKIM, DMARC) on each subdomain and a 'warming up' process are essential for maximizing deliverability.
Key opinions
- Segmentation Improves Reputation: Using subdomains to segment email traffic (marketing vs. transactional) helps isolate reputation problems, preventing one type of email from negatively impacting the deliverability of others.
- Authentication is Key: Proper setup of SPF, DKIM, and DMARC on each subdomain is crucial for authentication and improved deliverability.
- Warming Up Subdomains: Gradually warming up new subdomains is essential to establish a positive sender reputation and avoid being marked as spam.
- Sub vs Sub-Subdomain Limited Impact: The distinction between subdomains and sub-subdomains has a limited impact on deliverability, its main purpose is for organisation.
Key considerations
- Organizational Structure: Consider the organizational benefits of using subdomains, such as assigning a subdomain to a specific ESP or further subdividing mail streams.
- Monitoring Reputation: Actively monitor the reputation of each subdomain to identify and address deliverability issues promptly.
- Authentication Setup: Ensure correct and consistent SPF, DKIM and DMARC settings across all subdomains.
- Warming up Strategy: Implement a structured subdomain warmup strategy to slowly build a good reputation.
Marketer view
Email marketer from SparkPost recommends using subdomains to separate different types of mail streams (e.g., transactional, marketing) to maintain a good sender reputation for each type of communication.
2 Dec 2024 - SparkPost
Marketer view
Email marketer from Email Geeks explains that as an ESP, they like to use the subdomain for signing and sub-subdomain for tracking. This allows the customer to enter one set of NS records, and the ESP can manage all the DNS settings, secure tracking links, etc., from there. Some customers use the subdomain for signing in the 5322.from, which can be useful for reply management features.
21 Apr 2022 - Email Geeks
What the experts say
3 expert opinions
When considering the impact of subdomains and sub-subdomains on email deliverability, it's essential to focus on proper authentication and reputation management. While there's no inherent deliverability advantage to using sub-subdomains over subdomains, ensuring that authentication protocols (SPF, DKIM, DMARC) are correctly implemented on each subdomain is critical. Furthermore, each subdomain's reputation must be managed independently, as a poor reputation on one can negatively impact others within the same domain.
Key opinions
- No inherent deliverability benefit: There's no inherent deliverability advantage of using sub-subdomains over subdomains.
- Authentication is Critical: Correct implementation of SPF, DKIM, and DMARC on each subdomain is essential for deliverability.
- Reputation Management: Each subdomain's reputation should be managed independently.
Key considerations
- Authentication Setup: Carefully configure SPF, DKIM, and DMARC records for each subdomain to ensure proper authentication.
- Reputation Monitoring: Implement monitoring and management practices to maintain a positive reputation for each subdomain.
- Isolation of Issues: Consider using subdomains to isolate different types of email traffic, but be aware that issues on one subdomain can still impact the overall domain's reputation if not managed correctly.
Expert view
Expert from Email Geeks explains that deliverability-wise, there is no specific benefit in using a sub-subdomain compared to a subdomain.
7 Jun 2024 - Email Geeks
Expert view
Expert from Word to the Wise discusses the importance of managing the reputation of each subdomain separately. They explain that a poor sending reputation on one subdomain can negatively affect the deliverability of emails sent from other subdomains within the same domain.
1 Jul 2022 - Word to the Wise
What the documentation says
5 technical articles
Using subdomains in email marketing offers enhanced control over authentication protocols like SPF, DKIM, and DMARC, which directly impacts deliverability. Subdomains enable the differentiation of sending streams and necessitate tailored SPF configurations. Proper setup of authentication is critical for passing checks and maintaining sender reputation, as emphasized by various documentation sources.
Key findings
- Granular Control: Subdomains allow for more granular control over SPF and DKIM records.
- Sender ID Differentiation: Subdomains can differentiate sending streams for Sender ID validation.
- Custom SPF: Different subdomains require different SPF configurations due to how the `MAIL FROM` address is evaluated.
- DMARC Alignment: Subdomains are commonly used for DMARC alignment, crucial for passing authentication checks.
- Authentication Essential: Proper configuration of SPF and DKIM on subdomains is essential for achieving good deliverability.
Key considerations
- Authentication Setup: Ensure correct and consistent SPF, DKIM, and DMARC settings across all subdomains.
- SPF Configuration: Configure SPF records based on the specific requirements of each subdomain's sending stream.
- Monitoring Compliance: Regularly monitor authentication compliance to maintain deliverability.
Technical article
Documentation from RFC Editor (RFC 4406) explains that subdomains can be used to differentiate sending streams for Sender ID validation, potentially impacting deliverability based on sender reputation.
16 Sep 2022 - RFC Editor
Technical article
Documentation from Google Workspace Admin Help explains that using subdomains allows for more granular control over SPF and DKIM records, which can enhance email authentication and improve deliverability.
2 Jan 2025 - Google Workspace Admin Help
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