Summary
The ideal number of subdomains varies based on the complexity and volume of your email program. While some experts suggest limiting it to 3-4 for easier maintenance, others emphasize that there's no hard limit. The key is to segment email traffic effectively to protect your main domain's reputation and build independent reputations for different email streams (transactional, marketing, notifications, etc.). Naming conventions should be clear and reflect the purpose of each subdomain. DKIM signing is crucial for authenticating subdomains and managing their reputation. Ultimately, maintaining high deliverability across all subdomains is more important than the precise number you use.
Key findings
- No One-Size-Fits-All: The number of subdomains needed is highly dependent on the specific organization and its email strategy.
- Segmentation is Key: Using subdomains allows for effective segmentation of email traffic based on type (e.g., transactional, marketing).
- Reputation Isolation: Subdomains enable the building of separate sending reputations, improving overall deliverability.
- Clear Naming: Subdomain naming conventions should be descriptive and easily understandable by recipients.
- DKIM Essential: DKIM signing is crucial for authenticating subdomains and managing their reputation independently.
Key considerations
- Program Complexity: The more complex your email program, the more subdomains you may need.
- Volume per Subdomain: Ensure sufficient email volume per subdomain to build a positive sending reputation. Consider 1-2k per month.
- Maintenance Burden: Consider the increased maintenance overhead associated with managing a large number of subdomains.
- Warming Up: Follow a proper warmup process for new subdomains to avoid deliverability problems.
- Monitoring is Crucial: Continuously monitor the reputation of each subdomain to identify and address deliverability issues.
- Geographic Considerations: For decentralized global teams, consider using subdomains per country if centralized control is limited.
- Avoid Bad Names: Avoid using subdomain names that could be flagged as spam or malicious.
What email marketers say
14 marketer opinions
The number of subdomains needed for email sending depends on the complexity and volume of your email program. There's no single right answer, but the primary goal is to isolate email traffic, protect your main domain's reputation, and build independent reputations for different email streams (transactional, marketing, etc.). Naming conventions should be clear, descriptive, and reflect the purpose of the subdomain. It's generally recommended to start with a few key subdomains based on function and expand as needed. Avoid using potentially harmful or misleading names.
Key opinions
- No Fixed Limit: There is no set limit to the number of subdomains you can create; it's dependent on your needs.
- Isolation: Subdomains allow for isolating different types of email traffic (transactional, marketing, etc.)
- Reputation Management: Each subdomain builds its own sending reputation, improving overall deliverability.
- Descriptive Naming: Naming conventions should be clear and reflect the purpose of the subdomain.
- DKIM Signing: Each subdomain should be signed with a matching DKIM key for authentication and reputation building.
Key considerations
- Program Complexity: The complexity of your email program should drive the number of subdomains you create.
- Email Volume: Ensure sufficient email volume per subdomain to build a positive sending reputation.
- Warming Up: Understand how to properly warm up new subdomains to avoid deliverability issues.
- Monitoring: Regularly monitor the sending reputation of each subdomain.
- Decentralized Teams: For decentralized global teams, using subdomains per country might be appropriate if control over sending practices is limited.
- Brand Safety: Avoid using subdomain names that could be perceived as malicious or misleading.
Marketer view
Email marketer from ActiveCampaign answers that Subdomains should be named clearly so recipients can easily understand their purpose (e.g., 'promotions.yourdomain.com'). There is no recommended number, just appropriate names for email streams.
15 Jun 2023 - ActiveCampaign
Marketer view
Marketer from Email Geeks advises against using potentially problematic subdomain names like virus.domain.com or spam.domain.com. They emphasize the importance of understanding how to warm up a new subdomain, even on a shared IP pool.
12 Nov 2021 - Email Geeks
What the experts say
3 expert opinions
The responses suggest that the number of subdomains needed for email sending can vary widely. Some experts believe that most companies don't need more than 3-4 subdomains due to increased maintenance overhead. Others have observed successful brands using a range from one to many subdomains. Regardless of the number, maintaining high deliverability across all subdomains is crucial. Real-world examples show various subdomain patterns used in email addresses.
Key opinions
- Variable Needs: The required number of subdomains depends on the specific organization and email strategy.
- Maintenance Overhead: A large number of subdomains can increase maintenance efforts.
- Deliverability is Key: Maintaining high deliverability is more important than the specific number of subdomains.
- Diverse Patterns: Various subdomain patterns exist, including functional (support), client-based, or general email-related subdomains.
Key considerations
- Organizational Complexity: Consider the complexity of your email programs and organizational structure when deciding on the number of subdomains.
- Resource Availability: Assess your capacity to manage and monitor deliverability across multiple subdomains.
- Deliverability Focus: Prioritize strategies for maintaining high deliverability across all subdomains, regardless of their number.
- Example Inspiration: Look at examples from other companies to understand potential subdomain naming and structural patterns.
Expert view
Expert from Email Geeks confirms seeing Indeed use subdomains in email from addresses and that they have observed a variety of subdomain patterns in client data, such as localpart@e.whatever.example, reply.clientdomain.example, email.otherclient.example, and support.yetanotherclient.example.
17 Jan 2024 - Email Geeks
Expert view
Expert from Email Geeks suggests that most companies need no more than 3 or 4 different subdomains and many subdomains increases maintenance.
17 Dec 2022 - Email Geeks
What the documentation says
3 technical articles
Email deliverability documentation emphasizes the use of subdomains for managing sender reputation and segmenting email traffic. Google recommends using separate subdomains to protect the primary domain's reputation, particularly for marketing emails. RFC 6376 highlights that DKIM signing on subdomains facilitates independent reputation management, prioritizing authentication over a specific subdomain limit. Microsoft emphasizes the importance of segmenting email types via subdomains to improve deliverability. Although a precise number of subdomains isn't defined, the focus is on using them strategically for email purpose and authentication.
Key findings
- Reputation Protection: Subdomains help protect the primary domain's reputation, especially for marketing emails.
- Independent Management: DKIM signing on subdomains enables independent reputation management.
- Segmentation Importance: Segmenting email types using subdomains is crucial for deliverability.
- Purpose-Driven Domains: Focus on aligning subdomain use with email purpose, not a fixed number.
Key considerations
- Authentication: Implement DKIM signing on all subdomains to ensure proper authentication.
- Traffic Segmentation: Identify different email streams (e.g., marketing, transactional) and assign them to appropriate subdomains.
- Reputation Monitoring: Monitor the reputation of each subdomain to identify and address deliverability issues.
- Google Guidelines: Adhere to Google's Postmaster Tools guidelines for bulk email sending and subdomain usage.
Technical article
Documentation from RFC 6376 explains that using DKIM signing on subdomains allows for independent reputation management. They do not limit the number of subdomains, focusing instead on proper authentication.
18 Jan 2023 - RFC 6376
Technical article
Documentation from Google Postmaster Tools explains that using a separate subdomain for marketing emails can help protect the reputation of your primary domain. They do not specify a number, but advise on using different domains based on email purpose.
15 Feb 2025 - Google Postmaster Tools
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