Summary
Companies use cousin domains for a multitude of reasons, stemming from technical advantages, political and organizational challenges, or a desire to circumvent limitations. While some aim to protect their primary domain's reputation by separating marketing and transactional email streams, others seek to simplify management, bypass sending limits imposed by ESPs, or gain more control over email marketing operations. However, experts caution against relying on cousin domains as a band-aid solution, emphasizing that they don't address underlying sending issues and can even harm reputation by signaling an attempt to evade spam filters. Inbox providers might also group cousin domains, negating any intended benefits. It can also be attributed to internal politics, and the potential for conflicting motivations between IT and marketing teams.
Key findings
- Reputation Isolation: Protecting the primary domain's reputation from potentially harmful marketing campaigns or high-volume email streams.
- Management Simplification: Easing the management of different email types (transactional, marketing) by isolating them onto separate domains.
- Circumventing Limits: Bypassing sending limits imposed by email service providers.
- Technical Advantages: The ability to run tests on DMARC policies without impacting primary mail flows.
- Organizational Factors: Conflicting motivations between IT and marketing teams, leading to differing approaches to email infrastructure.
- Negative Signals: Using cousin domains can be interpreted as an attempt to circumvent spam filters.
- Expert Hesitation: Experts caution against relying on cousin domains as a replacement for fixing underlying issues in sending practices.
Key considerations
- Reputation Impact: Weigh the potential negative impact on your sending reputation if cousin domains are perceived negatively by inbox providers.
- Underlying Issues: Address underlying deliverability problems instead of relying solely on cousin domains as a workaround.
- Configuration and monitoring complexity: The complexity of maintaining and monitoring multiple domains' authentication setups (SPF, DKIM, DMARC).
- Expert advice: Consider the expert opinion that advises against it.
- Internal politics: Factor in internal politics which might point to issues in company culture
What email marketers say
9 marketer opinions
Companies use cousin domains for email campaigns for a variety of reasons, including to protect the reputation of their primary domain by separating different email streams (transactional vs. marketing), to bypass sending limits imposed by email providers, and to simplify tracking and analytics. It also enables better brand perception, easier management of sending infrastructure, and allows for tailoring messaging to specific audience segments. Some use them as a quick fix to reputation issues of their primary domain or because of organizational constraints.
Key opinions
- Reputation Protection: Cousin domains are used to shield the primary domain's reputation from potential damage caused by marketing campaigns or less reputable email streams.
- Segmentation: Different domains or subdomains allow companies to segment email types (transactional, marketing) for better deliverability management.
- Bypassing Limits: Some companies use cousin domains to circumvent sending limits set by email service providers.
- Simplified Management: Managing separate domains can be perceived as simpler than handling complex DNS configurations for subdomains on the primary domain.
- Brand Perception: Using different domains can improve brand perception by tailoring the sender address to the email content.
- Tracking & Analytics: Distinct domains facilitate streamlined tracking and analytics for specific campaigns.
- Audience Tailoring: Multiple domains enable businesses to tailor messaging and branding to different audience segments, product lines, or geographic regions.
- Quick Fix: Some use cousin domains as a short-term solution instead of addressing underlying reputation issues with their primary domain.
Key considerations
- Complexity: Managing multiple domains can add complexity to email marketing operations.
- Reputation Alignment: Inbox providers may correlate cousin domains, negating reputation benefits if sending practices are poor across all domains.
- Authentication: Proper authentication (SPF, DKIM, DMARC) is crucial for each domain to ensure deliverability.
- Long-Term Strategy: Using cousin domains should be part of a broader, well-defined email marketing strategy, not just a quick fix.
- Brand Consistency: Maintaining brand consistency across multiple domains is essential for a positive customer experience.
- ISP perceptions: Check if using cousin domains can impact your reputation as it is a sign that you are trying to circumvent spam filters.
Marketer view
Email marketer from Mailjet.com explains that some companies use different domains or subdomains to segment email streams (transactional, marketing, etc.) to help manage reputation and prevent issues with one type of email affecting the deliverability of others.
3 Apr 2025 - Mailjet.com
Marketer view
Email marketer from Gmass.co explains that some companies use cousin domains to bypass sending limits imposed by email service providers. This allows them to send more emails per day/month than they could with a single domain.
13 May 2022 - Gmass.co
What the experts say
4 expert opinions
Experts generally advise against using cousin domains. While some companies do it to protect their primary domain's reputation, exert more marketing control, or because of internal company politics and a lack of understanding, it's often a short-sighted solution that doesn't address underlying sending issues. Inbox providers may group cousin domains together, and the practice can even negatively impact reputation by signaling an attempt to circumvent spam filters.
Key opinions
- Generally Discouraged: Experts largely advise against using cousin domains as a long-term solution.
- Reputation Protection (Perceived): One perceived benefit is shielding the primary domain from reputation damage.
- Internal Politics: Internal factors like IT/marketing conflicts and a lack of understanding can drive the decision.
- Circumvention Attempt: Using cousin domains can be interpreted as an attempt to evade spam filters, harming reputation.
- Underlying Issues: Cousin domains don't solve the root causes of sending problems.
- Inbox Provider Grouping: Inbox providers may group cousin domains for reputation purposes, diminishing the intended benefits.
Key considerations
- Reputation Damage: Consider the potential negative impact on reputation due to the perception of spam filter evasion.
- Root Cause Analysis: Instead of relying on cousin domains, focus on identifying and fixing underlying sending problems.
- Internal Alignment: Address internal conflicts and knowledge gaps that contribute to the decision to use cousin domains.
- Long-Term Strategy: Develop a comprehensive email marketing strategy that prioritizes sender reputation and deliverability best practices instead of short-term fixes.
- Holistic approach: Consider that Inbox providers often group these together and you might not be solving a problem just making a new one
Expert view
Expert from Spam Resource explains that using cousin domains doesn't solve underlying sending problems and that inbox providers often group them together for reputation purposes anyway. It can also damage your reputation as it is a sign that you are trying to circumvent spam filters.
8 Apr 2023 - Spam Resource
Expert view
Expert from Word to the Wise explains that senders use cousin domains for various reasons, including internal politics, the desire to send mail without impacting the reputation of their primary domain, and a lack of understanding about the impact of their sending behavior. They also mention that marketing departments sometimes want more control than IT is willing to give them.
17 Jan 2025 - Word to the Wise
What the documentation says
4 technical articles
Documentation sources indicate that companies use cousin domains primarily for management and reputation isolation purposes. Different domains or subdomains can ease management of different email classes (marketing vs transactional) and protect the main domain's reputation by isolating bulk email streams. This setup also helps in testing DMARC policies without disrupting the primary mail flow and can reflect different aspects of a business while simplifying email addresses.
Key findings
- Reputation Isolation: A key reason is to isolate the reputation of different mail streams, such as marketing versus transactional emails, protecting the main domain's deliverability.
- Simplified Management: Using different domains eases management of different classes of mail.
- DMARC Testing: Subdomains or different domains facilitate testing DMARC policies without affecting primary mail flow.
- Reflect Business Structure: Multiple domains can represent different parts of a business or simplify email addresses.
- Bulk Email Management: A dedicated domain for bulk emails helps protect the reputation of the main domain.
Key considerations
- Authentication: Ensure proper authentication (SPF, DKIM, DMARC) is configured for all domains to maintain deliverability.
- Monitoring: Monitor the reputation of each domain separately to identify and address any deliverability issues.
- Configuration Complexity: Setting up and managing multiple domains can increase the complexity of email infrastructure.
- User Experience: Maintain a consistent user experience across different domains to avoid confusion or mistrust.
- Policy Alignment: Ensure email policies and practices align across all domains to prevent inconsistencies or compliance issues.
Technical article
Documentation from Google suggests that using a dedicated domain for sending bulk emails can help protect the reputation of your main domain. This also helps to ensure that important transactional emails are delivered reliably.
1 Jul 2022 - support.google.com
Technical article
Documentation from dmarc.org explains that subdomains can be helpful to isolate sending streams, and to test DMARC policies without affecting mail flow for your primary domains.
4 Nov 2022 - dmarc.org
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