Summary
Using subdomains for email sending is a strategic decision that impacts deliverability and sender reputation. By segmenting different email streams, like marketing, transactional, or sales emails, onto unique subdomains, businesses can better manage their sending practices and mitigate risks. This approach allows for isolated reputation building, meaning issues on one subdomain (e.g., high spam complaints from promotional emails) are less likely to negatively affect the deliverability of critical communications sent from another subdomain (like password resets or shipping notifications). Properly implementing and warming up these subdomains is crucial for success, ensuring internet service providers (ISPs) trust your sending practices across all your email types.
Key findings
- Reputation isolation: Subdomains allow you to isolate the reputation of different email sending streams, protecting your primary domain from potential deliverability issues on less-engaged email types.
- Deliverability improvement: Segmenting email traffic onto subdomains can lead to improved overall deliverability by allowing ISPs to assess each stream independently.
- Required warming: Just like new primary domains, new subdomains require a careful warming-up process to build a positive sending reputation with ISPs.
- Branding consistency: Subdomains help maintain consistent branding compared to using entirely separate, unrelated domains for different email purposes.
Key considerations
- Email volume: The decision to use subdomains often depends on the volume of emails sent from each stream; higher volumes benefit more from separation.
- Types of email: It is best practice to separate high-risk or high-volume email types (like marketing or cold outreach) from critical transactional emails using different subdomains.
- Future growth: Plan your subdomain strategy early to ensure a scalable and maintainable email infrastructure as your company grows. This foresight can prevent major deliverability issues down the line, as discussed in our guide on how email sending practices impact domain reputation.
- DNS records: Proper configuration of DNS records, including SPF, DKIM, and DMARC, is essential for each subdomain. Learn more about the basics of DMARC, SPF, and DKIM.
- Deliverability impact: While subdomains can help, they also carry their own reputation. A comprehensive guide on the basics of email subdomains explains how they work with deliverability.
What email marketers say
Email marketers widely acknowledge the benefits of using subdomains for managing their sending infrastructure. They often see subdomains as a crucial tool for maintaining brand consistency, protecting their main domain's reputation, and improving the overall deliverability of their diverse email campaigns. The consensus is that isolating different email streams, especially high-volume or potentially risky ones, is a proactive measure that prevents deliverability issues from cascading across all email communications.
Key opinions
- Brand integrity: Using subdomains helps maintain a consistent brand identity, unlike cousin domains which can dilute branding and train recipients incorrectly.
- Deliverability enhancement: Many marketers find that subdomains significantly improve email deliverability and help prevent important emails from going to spam folders.
- Organizational structure: Subdomains provide a clear structure for organizing and managing different types of email, such as transactional, marketing, and sales communications.
- Reputation safeguarding: The primary reason for many marketers to use subdomains is to protect their root domain’s reputation from potential negative impacts caused by specific email campaigns (e.g., marketing emails receiving high complaint rates).
Key considerations
- Strategic planning: It is beneficial to decide on a subdomain strategy early in your company’s growth to have a sensible plan for future email streams and providers.
- Growth sustainability: Marketers consider whether sending all email types from a generic company domain is sustainable as the business scales, often finding it is not.
- Avoiding sharing: Sharing a single domain for all email types is generally seen as a bad practice for deliverability and reputation management.
- Purpose-driven segmentation: Marketers often segment email types like sales, marketing, and support onto different subdomains for better management and reputation control. Explore more about using separate subdomains for transactional and promotional emails.
Marketer view
Email marketer from Email Geeks asked about the purpose of using subdomains for sending emails, their effect on reputation, and whether they require a warning period.
Marketer view
Marketer from Email Geeks suggested that sharing a single domain for all email types is generally detrimental, but using subdomains is a less harmful alternative. They also emphasized the need to warm up new subdomains.
What the experts say
Deliverability experts consistently advocate for the strategic use of subdomains, emphasizing their role in reputation management and long-term email program health. They highlight that while subdomains do inherit some reputation from the parent domain, their primary value lies in isolating different mail streams to prevent a single campaign's poor performance from jeopardizing the entire domain's sending ability. Experts also underline that the decision to implement subdomains often involves a blend of technical requirements and broader business strategy, stressing the importance of clear policies and careful warming.
Key opinions
- Reputation isolation: Subdomains are a great way to silo off reputation from a core branded root domain, as detailed in this Kickbox article on sending domains.
- SPF alignment necessity: You will always need a subdomain for SPF alignment at ESPs, even if it is just a bounce domain that users never see.
- Inherited reputation: New subdomains inherit some of the reputation of the parent domain, meaning a bad enough parent reputation can still hurt delivery on the new subdomain.
- No universal solution: There isn't a single subdomain strategy that is right for every company; decisions should be tailored to specific needs.
Key considerations
- Business vs. delivery decisions: Many decisions regarding subdomain usage are more about maintainability, ease of use, and overall business strategy than purely technical deliverability concerns.
- Early decision-making: It is sensible to make early decisions about your subdomain approach so that you have a plan in place as your email program evolves and grows. Read more on when to implement email subdomains for deliverability.
- DKIM considerations: Consider whether you want every provider to use your primary domain for DKIM authentication or if different subdomains should have their own DKIM configurations (e.g., marketing versus support).
- Parent domain impact: Understand that the parent domain's reputation can indeed influence subdomain deliverability. Our guide on how parent domain reputation affects subdomain deliverability provides deeper insight.
Expert view
Deliverability expert from Email Geeks suggested that if an email program is currently performing well, there's an argument against making changes. However, it is also important to plan a sensible subdomain approach for future mail streams and providers as the business grows.
Expert view
Deliverability expert from Email Geeks clarified that a subdomain is always necessary for SPF alignment with Email Service Providers (ESPs). They noted this is typically the bounce domain, which remains unseen by users.
What the documentation says
Official email documentation and industry research consistently support the use of subdomains as a best practice for managing sender reputation and optimizing deliverability. These resources highlight that subdomains allow for effective segmentation of email traffic, preventing issues with one type of email (e.g., marketing) from negatively affecting the deliverability of others (e.g., transactional). Furthermore, documentation often points out that subdomains, while new, can benefit from the established age and reputation of their main domain, providing a smoother ramp-up for new sending streams.
Key findings
- Top sender practice: Leading email senders commonly use subdomains to organize different email types and protect their core domain’s reputation.
- Traffic isolation: Subdomains significantly enhance email deliverability by allowing distinct email traffic types to be isolated, which helps maintain a good sender reputation.
- Age inheritance: A subdomain inherits the age and some reputation of its main domain, which is vital because many email providers view newer, unproven domains with suspicion.
- Effective management: Using an email subdomain allows for more effective separation and management of sender reputation, protecting the main domain from potential issues.
Key considerations
- Structured organization: Subdomains provide a clear structure for organizing and managing various email categories, contributing to better overall email strategy.
- Optimized deliverability: Implementing distinct email subdomains is a key factor in enhancing your email strategy and improving inbox placement rates.
- Technical tool: A subdomain is considered a powerful technical tool to secure email reputation, optimize deliverability, and effectively segment sending flows.
- Strategic implementation: It is important to understand the 'when, why, and how' of using subdomains to maximize their benefits for email deliverability and management.
Technical article
Mailgun documentation explains that email subdomains are used by top senders to provide a clear structure for organizing various email types, effectively protecting domain reputation and improving overall email deliverability.
Technical article
Mailmodo documentation indicates that email subdomains help protect sender reputation and improve email deliverability by providing a clear structure for organizing different types of emails.
Related resources
15 resources
Related pages
Why use subdomains for email marketing deliverability?
Why use email subdomains and when to implement them for deliverability?
Can negative email engagement on a subdomain affect the primary domain's reputation?
How does parent domain reputation affect subdomain deliverability and sender reputation?
Should I use separate email subdomains for transactional and promotional emails, and how does engagement affect this?
A simple guide to DMARC, SPF, and DKIM
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A practical guide to understanding your email domain reputation
