How many subdomains should I create for my email sending, and what naming conventions should I use?

Key findings

• No strict limits: The number of subdomains you can create is generally unlimited, often depending on your hosting plan. However, fewer subdomains might be better for manageability.
• Reputation isolation: Using subdomains allows different email streams (e.g., transactional, marketing) to build independent reputations, protecting your primary domain if one stream experiences deliverability issues.
• Functional naming: Naming subdomains based on their function (e.g., news.yourdomain.com, alerts.yourdomain.com) is a best practice for clarity and organization.
• Volume considerations: Each subdomain needs a consistent, minimum volume of email traffic (e.g., 1-2k per month) to build and maintain a reputable sending history with mailbox providers.

Key considerations

• Avoid fragmentation: Over-fragmenting subdomains can lead to insufficient volume per subdomain, hindering reputation building and increasing management complexity.
• Naming cautions: Refrain from using suspicious terms like virus or spam, or using another brand's name without proper authorization, as these can trigger blocklists (or blacklists) and spam filters.
• Warming up: New subdomains, even on shared IP pools, require a careful warming-up process to establish a positive sender reputation.
• Ongoing monitoring: Each subdomain's sending reputation needs continuous monitoring and management to ensure optimal deliverability.

Key opinions

• Functional segmentation: Many marketers advocate for using subdomains to separate different types of email (e.g., transactional, marketing, alerts) to isolate potential deliverability issues.
• Brand relevance in naming: Naming subdomains with clear, descriptive prefixes helps maintain brand consistency and aids recipient recognition, such as email or updates.
• Manageable numbers: While technically unlimited, marketers often find that a few well-defined subdomains are sufficient, as too many can complicate management and dilute individual reputations.
• Protecting the root domain: Subdomains are seen as essential for protecting the primary domain's reputation, especially for sensitive or high-volume sending.

Key considerations

• Warming up: Proper warming for new subdomains is frequently overlooked but critical for establishing a good sending history.
• Centralized vs. decentralized teams: The organizational structure influences subdomain strategy; decentralized teams might benefit from regional subdomains, while centralized teams can consolidate.
• DNS configuration: Proper DNS record configuration for each subdomain is vital for email authentication.
• Ease of management: The complexity of managing multiple subdomains and their reputations should be a factor in determining how many to create. Consider how sender addresses are created for new subdomains.

Key opinions

• Strategic segmentation: Subdomains are best used for segmenting different email types (e.g., transactional, marketing) to ensure independent reputation building and risk isolation.
• Avoid suspicious naming: Names like spam or virus should never be used, as they immediately signal malicious intent to mailbox providers and blocklists (or blacklists).
• Warm-up importance: Every new subdomain requires a dedicated warming period to establish credibility, even when using shared IP pools.
• Manageable quantity: Most companies rarely need more than a handful of subdomains, as an excessive number can lead to reputation dilution and increased management complexity.

Key considerations

• Maintenance overhead: More subdomains translate directly into more administrative and monitoring work, which must be factored into resource allocation.
• Business structure impact: Decentralized global teams might genuinely benefit from regional or specific business unit subdomains to maintain control over their sending practices.
• Brand and trademark protection: Never use another brand's name in your subdomain, even if licensed, to avoid potential confusion or legal issues that could harm your own domain's reputation.
• DNS records and authentication: Proper configuration of DNS records, including DKIM keys for each subdomain, is essential for independent reputation building. For further reading, check EmailLabs' guide to mastering email subdomains.

Key findings

• Unlimited creation: Most hosting and email service providers allow the creation of an unlimited number of subdomains under a root domain.
• Reputation independence: Each subdomain can accrue its own sender reputation, distinct from the root domain and other subdomains, which helps in isolating deliverability issues.
• DNS record requirements: Proper configuration of DNS records, including SPF, DKIM, and DMARC, is mandatory for each email-sending subdomain to ensure authentication and deliverability.
• Descriptive naming: Naming conventions should be clear and descriptive, reflecting the purpose of the emails sent from that subdomain for better organization and recognition.

Key considerations

• Technical setup: Setting up subdomains requires specific technical steps for DNS records, which are crucial for email routing and authentication.
• Managing traffic: Implementing proper accounts, aliases, and forwarding rules within each subdomain is essential for successfully handling email traffic.
• Consistency and organization: A consistent naming strategy is crucial for internal organization and external perception, ensuring clarity across all email communications.
• Compliance and best practices: Adhering to subdomain best practices, including descriptive naming and correct DNS configuration, improves deliverability and engagement.