What is the best practice for selecting a subdomain for marketing emails and how does it impact deliverability?

Key findings

1. Reputation isolation: Using a dedicated subdomain for marketing emails helps protect your primary domain's reputation. If marketing campaigns encounter deliverability issues (e.g., higher spam complaints), the impact is contained to the subdomain, safeguarding the main domain used for transactional or critical communications.
2. Indirect deliverability impact: While the subdomain name itself doesn't directly affect deliverability, how it's used can. A descriptive or brand-aligned subdomain can enhance recipient recognition and engagement, which in turn positively influences sender reputation and inbox placement. This is a key reason why many choose to use a subdomain for marketing.
3. DNS configuration is key: Proper configuration of DNS records, including SPF, DKIM, and DMARC, is far more critical than the subdomain name for deliverability. These authentication protocols confirm your legitimacy as a sender. You can read more about the basics of email subdomains and their setup.
4. Common naming conventions: Simple and common subdomains like 'email', 'mail', 'e', or 'm' are widely used and easily recognizable. However, some brands opt for more creative or memorable subdomains to align with their marketing strategy.

Key considerations

1. Brand alignment: Choose a subdomain that resonates with your brand identity and is easy for recipients to recognize and trust. While functional names are common, a unique, brand-specific subdomain can enhance brand recall.
2. Recipient visibility: Recipients will see your subdomain as part of the 'From' address. Ensure it's professional, clear, and doesn't appear suspicious. This visibility impacts the recipient's perception and their likelihood of engaging with your emails.
3. Segmentation: For advanced email strategies, consider using different subdomains for various email types, such as marketing, transactional, and promotional messages. This further isolates reputation and allows for more granular management of sender identity, which is key to improving deliverability using subdomains.
4. Avoid existing use: Before finalizing a subdomain, check that it's not already in use for other purposes, which could lead to conflicts or confusion.

Key opinions

1. No direct deliverability impact: Many marketers believe the subdomain name itself doesn't directly influence inbox placement. Deliverability is more affected by overall domain reputation and sending practices.
2. Branding and engagement: The choice of a subdomain can be an extension of a branding strategy. A creative or memorable subdomain can increase recipient engagement, which indirectly boosts deliverability by signaling positive sender behavior to ISPs.
3. Segmentation benefits: Marketers frequently recommend using separate subdomains for different types of email (e.g., marketing, transactional, password resets). This segmentation helps isolate the reputation of each email stream, minimizing risks. It's about deciding when to implement subdomains.
4. Recipient perception: Recipients see the subdomain in the 'From' address. Choosing a clear, non-offensive, and professional name helps build trust and familiarity.

Key considerations

1. Ease of recognition: Simple and common subdomain choices like 'email.', 'mail.', or 'm.' are effective because they are instantly recognizable to recipients.
2. Long-term commitment: Marketers should consider their subdomain choice carefully as it becomes a fixed part of their sending identity. Changing it later can be disruptive.
3. Testing new subdomains: Before fully deploying a new subdomain, it's advisable to test it with a smaller audience to ensure it functions as expected and maintains deliverability. This practice is highlighted in SMTP2GO's guidance on email subdomains.
4. Reputation building: Regardless of the name, the new subdomain will need to build its own sending reputation. Consistent, positive sending behavior is crucial for this. For this reason, subdomains are generally recommended.

Key opinions

1. Technical configuration is key: Experts stress that DKIM signing domain matching the 5322.From header is far more important for deliverability than the subdomain's name. Proper authentication is non-negotiable.
2. Reputation shielding: Using subdomains is a best practice for protecting the root domain's reputation. If a subdomain used for marketing encounters issues like being added to a blacklist (or blocklist), the primary domain remains largely unaffected, preserving critical communication channels.
3. Strategic segmentation: It's best practice to use different subdomains for various email functions, such as marketing, transactional, and password resets. This allows for independent reputation management for each stream, which is crucial for optimal deliverability. You can learn more about the best DMARC, DKIM, and SPF setup.
4. Domain age and warmup: New subdomains need to build their own reputation. This involves a gradual warming-up process, regardless of the chosen name, which is a key consideration for overall sender performance.

Key considerations

1. Authentication alignment: Ensure that your DMARC, DKIM, and SPF records are correctly set up for the chosen subdomain to pass email authentication checks. This is paramount for avoiding spam filters and enhancing trust with ISPs. A simple guide to email authentication can help.
2. Avoid common pitfalls: While creative names are possible, avoid choices that could be misinterpreted or appear suspicious. Simplicity and professionalism generally serve deliverability better than overly obscure or playful names.
3. Monitoring is essential: Regardless of subdomain choice, continuous monitoring of deliverability metrics (e.g., bounce rates, complaint rates, inbox placement) is crucial. This helps in promptly identifying and addressing any issues that might arise. Iterable offers insights into key considerations for root domains versus subdomains.
4. Long-term strategy: Consider your long-term email sending strategy when choosing a subdomain. It should support future growth and segmentation needs, ensuring scalability and sustained deliverability performance.

Key findings

1. Authentication is paramount: Documentation stresses that authenticating emails with SPF, DKIM, and DMARC is fundamental. The subdomain must have these records properly configured for successful delivery.
2. Reputation segmentation: Industry best practices encourage using separate subdomains for different email types (e.g., marketing, transactional) to isolate sender reputation. This prevents issues with one stream from affecting others.
3. Clear naming for clarity: Documentation advises using clear and concise subdomain names to avoid confusion and enhance recipient recognition. Simplicity often outperforms complexity.
4. Compliance with ISP policies: Adherence to ISP-specific sending policies and guidelines is crucial. Even with a well-chosen subdomain, non-compliance can lead to deliverability issues.

Key considerations

1. DNS record accuracy: Ensure all DNS records for the subdomain (SPF, DKIM, DMARC, MX records) are correctly published and validated. Errors here can severely impact deliverability. This aligns with best practices for DNS lookups and subdomain usage.
2. Header alignment: The domain in the 'From' header (RFC 5322.From) should align with the DKIM signing domain for optimal DMARC pass rates. This is a crucial technical detail that affects deliverability, as detailed in discussions about what RFC 5322 says.
3. Domain warming: New subdomains require a structured warming-up period to build a positive sending reputation with ISPs. Gradual increases in volume and consistent engagement are key during this phase.
4. Feedback loops: Register your subdomain with ISP feedback loop programs. This allows you to receive notifications when recipients mark your emails as spam, helping you maintain a clean sending list and reputation. EmailLabs discusses mastering email subdomains.