What are cousin domains in email marketing?

Cousin domains are domain names that are similar to your main brand domain but not directly part of it (e.g., yourcompanymail.com instead of yourcompany.com ). They are often used with the intent of isolating sender reputation for different email streams or to gain more flexibility in DNS management outside of the main domain's strict controls.

What are the disadvantages of using cousin domains?

While they might offer perceived benefits like reputation isolation for riskier email campaigns, they typically lead to negative consequences. These include recipient confusion, increased spam complaints, a higher likelihood of emails landing in spam folders due to phishing-like appearances, and a general erosion of brand trust. Using them can actually hurt your overall deliverability, making ISPs less strict with them .

What is a better alternative to cousin domains for email campaigns?

The recommended approach is to use subdomains (e.g., marketing.yourcompany.com ) instead of cousin domains. Subdomains maintain brand consistency while allowing you to segment your sending reputation. If one subdomain encounters deliverability issues, it typically does not affect the reputation of your main domain or other subdomains. This strategy provides both control and brand integrity.

How can I protect my email domain's reputation?

To protect your domain's reputation, ensure all your sending domains and subdomains have correctly configured email authentication records (SPF, DKIM, DMARC). Monitor your domain's health using tools like Google Postmaster Tools . Most importantly, maintain good sending practices: send relevant content to engaged subscribers, clean your lists regularly, and avoid sending to old or unverified addresses.

Why do companies use cousin domains for email campaigns? - Sender reputation - Email deliverability - Knowledge base

Q: Should transactional and marketing emails be sent from separate domains or subdomains?

Yes, it is highly recommended. Separating transactional and marketing emails to different subdomains or IP addresses helps protect the reputation of your primary domain. If your marketing emails, which might experience higher bounce or complaint rates, affect their dedicated subdomain, your crucial transactional emails from the main domain will remain unaffected, ensuring their reliable delivery.

When managing email campaigns, especially for large organizations, the question often arises: why do some companies use domains that are similar, but not identical, to their main brand domain? These are often referred to as cousin domains. While it might seem counterintuitive to stray from the primary brand identity, there are several perceived reasons why marketers and IT teams consider this approach. However, it's crucial to understand that while a company might choose this path, it often comes with significant downsides.

The practice of using cousin domains, such as "companymail.com" instead of "company.com," can appear to offer certain flexibilities. This is particularly true when dealing with the complexities of email deliverability and sender reputation. My goal here is to delve into these motivations, the risks involved, and better, more secure strategies for managing your email sending infrastructure.

The motivations behind using cousin domains

One of the primary reasons some companies might consider using a cousin domain is the perceived benefit of reputation isolation. Email service providers (ESPs) and internet service providers (ISPs) evaluate a sender's reputation based on various factors, including spam complaints, bounce rates, and engagement. If a particular email campaign or sending stream, like marketing newsletters or cold outreach, performs poorly, it can negatively impact the sender's domain reputation.

By using a cousin domain for these potentially higher-risk campaigns, the intention is to protect the reputation of the main brand domain. The logic is that if the cousin domain gets blocklisted (or blacklisted), the primary domain, used for transactional emails and official communications, remains unaffected. This separation aims to ensure critical emails continue to reach the inbox, while riskier email types might face deliverability challenges without jeopardizing the core business communication.

Another common driver is the desire for greater operational flexibility in DNS management. Changing DNS records on a main corporate domain can be a complex process, often requiring multiple approvals from IT security teams. This can lead to delays and potential errors, especially for marketing teams who need to quickly configure or adjust DNS settings for email authentication protocols like SPF, DKIM, and DMARC. A separate (cousin) domain might offer marketers more autonomy in managing these crucial records.

Some companies also argue that using a distinct domain helps differentiate email streams. For instance, transactional emails (receipts, password resets) might come from the main domain, while promotional emails come from a cousin domain. The idea is to help recipients identify the type of email at a glance, though this often backfires due to the inherent confusion it causes.

The inherent risks of cousin domains

Despite the perceived benefits, using cousin domains for legitimate email campaigns is generally ill-advised due to several significant risks. Firstly, it creates a lack of brand consistency and can confuse recipients. When an email arrives from a domain that isn't exactly the brand they expect, it immediately raises red flags. This can lead to lower open rates, increased spam complaints, and a damaged sender reputation overall, making your email deliverability worse, not better.

Perhaps the most critical issue is that cousin domains are a favored tactic of phishers and cybercriminals. These malicious actors create lookalike domains to trick users into thinking they are interacting with a legitimate brand. When a legitimate company also uses a similar-looking domain, it blurs the lines and makes it harder for recipients to distinguish genuine emails from phishing attempts. This puts your subscribers at higher risk of falling victim to scams, eroding trust in your brand. The M3AAWG Sending Domains Best Common Practices explicitly warn against cousin domains looking like phishing.

ISPs and email security systems are increasingly sophisticated in detecting and flagging emails that appear suspicious. Cousin domains often trigger these filters because they mimic the patterns of malicious phishing attempts. This can lead to your legitimate emails landing in spam folders or being blocked entirely, regardless of your content or sending practices. As a result, companies using cousin domains may find themselves struggling with deliverability and battling blocklists unnecessarily.

While some older practices suggested rotating between multiple domains to avoid spam filters, this is largely outdated and ineffective today. Instead, it often signals suspicious behavior to modern anti-spam systems, as noted in discussions about spammers using cousin domains. Trust and a consistent brand presence are far more valuable than perceived reputation isolation through a separate, confusing domain.

Better alternatives to cousin domains

Instead of resorting to cousin domains, a much more effective and secure strategy for managing email reputation and deliverability is the strategic use of subdomains. Subdomains, like marketing.yourcompany.com or newsletter.yourcompany.com, are part of your main domain but have their own distinct reputations. This allows for reputation segmentation without confusing recipients or appearing malicious.

Brand consistency: Subdomains maintain a clear connection to your main brand, reinforcing trust and recognition. Your recipients will immediately know the email is from your company.
Reputation isolation: If a subdomain experiences deliverability issues due to a specific campaign, your root domain's reputation, and other subdomains, remain protected. This is why many companies use subdomains for transactional and marketing email separation.
Easier DNS management: You can delegate DNS management for subdomains without affecting your main domain's critical records, addressing the flexibility concern. This makes it easier to set up email authentication protocols like DMARC, SPF, and DKIM for each sending stream.

To illustrate, if you have your main website at yourcompany.com, you might send transactional emails from no-reply@yourcompany.com and marketing newsletters from newsletter@marketing.yourcompany.com. This approach is widely considered a best practice for improving email deliverability and protecting your overall sender reputation.

Understanding how email blacklists actually work reinforces that maintaining a strong, unified brand identity across your primary domain and its subdomains is key. This approach builds long-term trust with recipients and ensures your emails consistently reach the inbox, rather than being flagged as suspicious or spam.

Views from the trenches

Best practices

Always prioritize using your main brand domain and its subdomains for all email sending.

Segment your email sending by purpose using different subdomains (e.g., `marketing.yourdomain.com`, `transactional.yourdomain.com`).

Implement strong email authentication (SPF, DKIM, DMARC) on all your sending domains and subdomains.

Regularly monitor your domain's reputation using tools like Google Postmaster Tools.

Common pitfalls

Using cousin domains: This practice is frequently mistaken for phishing, causing confusion and deliverability issues.

Ignoring conflicting motivations: Security and marketing teams often have different priorities regarding DNS changes.

Underestimating the impact of shared domains: Relying on ESPs to handle everything without proper domain setup can lead to problems.

Failing to educate senders: A lack of understanding about email protocols can lead to poor choices in domain usage.

Expert tips

Domain reputation is built over time with consistent, good sending practices, not by changing domains.

If you need to separate sending streams, subdomains are the accepted and secure method.

Security teams often prefer subdomains as they maintain a clear organizational hierarchy and control.

Ensure proper DNS delegation to give marketing teams flexibility with subdomains without compromising the root domain.

Expert view

Expert from Email Geeks says that using cousin domains, like Facebook does, is generally not a recommended practice.

2020-04-22 - Email Geeks

Marketer view

Marketer from Email Geeks says that marketers often seek more freedom to change DNS settings for campaigns, which is difficult with a main domain due to red tape and potential errors.

2020-04-22 - Email Geeks

Choosing the right domain strategy

While the immediate impulse might be to use cousin domains for reasons of reputation isolation or perceived ease of management, this approach introduces more problems than it solves. It undermines brand trust, increases the likelihood of emails being flagged as spam or phishing, and ultimately harms your overall email deliverability.

The long-term success of your email program hinges on maintaining a strong, consistent, and trusted sending identity. By leveraging subdomains and robust authentication protocols, you can achieve the desired separation for different email streams while ensuring your brand remains cohesive and your messages reliably reach their intended inboxes.