Summary
The use of 'cousin domains' in email campaigns, where a brand sends emails from a domain that is similar but not identical to its primary domain, is a practice fraught with deliverability risks. While some companies, even large ones, might adopt this strategy for various reasons, including internal organizational hurdles or a desire to isolate sending reputation, it generally contradicts established email deliverability best practices. The consensus among deliverability professionals is that cousin domains often confuse recipients and Internet Service Providers (ISPs), leading to increased spam complaints and blocklisting, ultimately harming sender reputation and inbox placement.
Key findings
- Reputation isolation: Companies sometimes use cousin domains to separate potentially lower-reputation marketing emails from their main corporate domain, aiming to protect the primary brand reputation.
- Internal friction: Organizational constraints, such as difficulty obtaining DNS changes for the primary domain from IT or legal departments, can push marketing teams towards using separate domains.
- Perceived flexibility: Marketers may believe that having a separate domain provides more freedom to manage their email sending infrastructure without impacting core business operations.
- Deliverability impact: Despite the perceived benefits, cousin domains are often flagged by ISPs as suspicious, increasing the likelihood of emails landing in spam folders or being blocked entirely, negatively affecting overall email deliverability.
- User confusion: Recipients often find emails from cousin domains confusing or suspicious, which can lead to higher spam complaint rates and a damaged brand image.
Key considerations
- Brand consistency: Maintaining brand consistency is crucial for building trust. Using a domain that differs from your primary brand identity can undermine this trust and lead to recipient skepticism.
- Phishing perception: Cousin domains closely resemble phishing attempts, where bad actors register similar domains to trick users. This similarity can lead to legitimate emails being flagged by spam filters or even by vigilant recipients as fraudulent.
- Subdomain alternative: A more effective and recommended approach for segmenting email traffic is to use subdomains (e.g., mail.yourcompany.com, marketing.yourcompany.com) that are clearly tied to the main domain. This allows for reputation segmentation while maintaining brand consistency.
- ISP scrutiny: ISPs are increasingly sophisticated in detecting and penalizing sending practices that mimic spam or phishing, making cousin domains a high-risk strategy. The M3AAWG (Messaging, Malware and Mobile Anti-Abuse Working Group) provides best practices that strongly advise against this approach, emphasizing the importance of alignment and consistency.
- Reputation management: Building and maintaining a strong domain reputation is a long-term investment. Using cousin domains can fragment this reputation and make it harder to manage effectively.
What email marketers say
Email marketers often face a dilemma: balancing aggressive campaign strategies with maintaining a clean sender reputation. While some marketers see benefits in using different domains to isolate risky campaigns or gain more control over DNS settings, others express concerns about brand confusion and the perception of phishing. The general sentiment is a cautious one, with many acknowledging the risks even if they understand the perceived operational advantages.
Key opinions
- Control over DNS: Some marketers feel that using a separate domain for email allows them more flexibility to manage DNS records (like SPF, DKIM, DMARC) without needing to involve the main IT department, which can be slow or resistant to changes on the primary brand domain.
- Reputation segmentation: A common motivation is to protect the primary corporate domain's reputation from the potential negative impacts of marketing email activities, especially for campaigns with higher perceived risk of spam complaints or bounces. This is often an attempt to segment sender reputation.
- Avoiding red tape: The bureaucratic hurdles within large organizations can make it challenging to implement necessary email configurations on the main domain, pushing marketers towards less conventional solutions.
- Brand perception: Some marketers acknowledge that while cousin domains might offer operational benefits, they can raise questions for recipients who might view them as less legitimate, potentially impacting engagement.
- Cold outreach: For cold email outreach, some marketers intentionally use separate or cousin domains to shield their main domain from the inherently higher risks associated with unsolicited communications.
Key considerations
- Subscriber trust: It's critical to consider how recipients perceive emails. A domain that looks slightly off or unfamiliar can erode trust, regardless of the sender's intentions. Even major brands like Facebook find it necessary to explain their use of different domains to prevent subscriber confusion and emails going to spam.
- Long-term deliverability: While a cousin domain might offer short-term isolation, it can hinder long-term deliverability by creating fragmented brand identity and making it harder for ISPs to recognize legitimate senders.
- Spam filter triggering: Many marketers observe that rotating between multiple domains or using less common ones can inadvertently trigger spam filters, which are designed to flag suspicious sending patterns.
- Alternative solutions: Instead of cousin domains, marketers should advocate for the proper implementation of subdomains (e.g., email subdomains) for different email types. This provides the necessary separation without the negative implications of cousin domains.
Email marketer from Email Geeks observes that while they were previously confident in using subdomains for different campaigns, the discovery of Facebook using an entirely different (cousin) domain for notifications raised concerns. This approach seems counter to typical best practices.
Email marketer from Email Geeks explains their understanding that cousin domains are sometimes used because marketers need greater flexibility to change DNS settings, which is often difficult to achieve with the main company domain due to internal bureaucracy or potential risks of errors impacting core services. This operational freedom is a key driver.
What the experts say
Email deliverability experts universally advise against the use of cousin domains. Their insights reveal that such practices are often driven by internal corporate politics or a misunderstanding of how ISPs assess sender reputation. Experts emphasize that cousin domains resemble phishing attempts, erode recipient trust, and ultimately harm deliverability by making senders appear less legitimate. They strongly advocate for subdomains as the proper method for segmenting email traffic without compromising brand integrity or deliverability.
Key opinions
- Avoid cousin domains: The direct and unequivocal advice from experts is to avoid using cousin domains for email sending because they are easily confused with phishing attempts.
- Internal evasion: Experts suggest that the use of cousin domains is often done to bypass or evade internal company rules and bureaucratic processes, rather than for legitimate external email deliverability reasons.
- Conflicting motivations: There's a fundamental conflict between corporate IT security's priorities and marketing's objectives, which can lead to marketers adopting risky domain strategies.
- ESP influence: Some Email Service Providers (ESPs) might inadvertently encourage the use of new domains (including cousin domains) because it is simpler for them to onboard clients with a fresh domain than to assist with complex subdomain setups on existing infrastructure.
- Subdomains vs. cousin domains: Experts distinguish between legitimate brand-aligned domains or subdomains used for campaigns and the problematic 'cousin domains,' emphasizing that the former are acceptable, while the latter are not.
Key considerations
- Sender education: A significant challenge is educating senders about best practices for domain usage, as it requires considerable dedication and effort from deliverability professionals.
- Perception of phishing: Using a cousin domain (e.g., email-domain.com instead of email.domain.com) makes emails look like phishing attempts, leading to higher spam classifications and potentially blocklisting.
- Best practices alignment: Adhering to industry best practices, such as those published by M3AAWG, is crucial for maintaining strong deliverability and avoiding issues related to domain usage.
- Risk mitigation: While companies aim to mitigate risk, using cousin domains often introduces new, more severe risks related to trust and deliverability. Proper subdomain setup, along with robust email authentication (SPF, DKIM, DMARC), is the safer alternative.
Expert from Email Geeks warns that what Facebook is doing, specifically using `facebookmail.com` instead of `facebook.com` for certain emails, falls under the category of 'cousin domains.' This practice is generally ill-advised and can lead to significant deliverability problems for most senders.
Expert from Email Geeks explains that ESPs might find it easier to onboard a sender with a new, separate domain rather than guiding them through the more complex process of setting up and configuring a subdomain on their existing primary domain. This convenience factor can sometimes lead to suboptimal domain strategies being adopted.
What the documentation says
Official documentation and industry best practices strongly caution against the use of cousin domains due to their resemblance to phishing attacks and the negative impact on trust and deliverability. These resources consistently recommend using subdomains linked to the main brand for different email purposes, ensuring consistent branding and clear authentication, which are critical for recipient recognition and ISP acceptance. Deviation from these guidelines increases the risk of emails being filtered as spam or blocked.
Key findings
- Phishing mimicry: Cousin domains are a known tactic in phishing and business email compromise (BEC) attacks, where fake websites or emails use similar domain names to legitimate ones to trick users.
- Anti-abuse guidelines:Industry bodies like M3AAWG publish best practices that advocate for aligning sending domains with the main brand to prevent confusion and abuse.
- User experience: Documentation emphasizes that clear, consistent sending domains are vital for user recognition and trust, minimizing the chances of emails being marked as spam.
- Reputation fragmentation: Using multiple, disconnected domains can dilute or fragment a sender's reputation, making it harder for ISPs to accurately assess and trust their sending behavior.
- Security implications: Cousin domains undermine security protocols like DMARC, SPF, and DKIM, which rely on clear domain alignment to verify sender authenticity and prevent spoofing.
Key considerations
- Brand integrity: Maintaining a unified brand presence across all communications, including email, is crucial for building credibility. Using cousin domains detracts from this and can lead to brand erosion.
- Policy enforcement: ISPs and email security providers often have policies and filters specifically designed to catch domains that are too similar to established brands but aren't legitimate subdomains, thereby blocking or flagging them.
- Authentication standards: Official documentation stresses the importance of proper email authentication. Cousin domains often fail to align with the primary domain's authentication, leading to 'soft fails' or rejections.
- Industry consensus: The collective wisdom from email organizations and security experts consistently advises against cousin domains, considering them a risky and generally unnecessary deviation from sound sending practices. This includes warnings from security firms about cousin domain attacks.
Documentation from Red Points defines a cousin domain attack as a type of phishing attack where a fake website with a domain name very similar to a legitimate website is created to trick users. This highlights why legitimate senders using 'cousin' domains inadvertently create a phishing-like appearance.
Documentation from Abion advises that the main aim of cousin domain attacks, as with most cybersecurity threats, is to dupe users into handing over sensitive information. Therefore, legitimate companies must avoid practices that could be mistaken for such attacks to protect their users and brand reputation.
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