Should I use subdomains for transactional and promotional emails to protect my main domain reputation?

Summary

The consensus among email experts and marketers is that using subdomains is a beneficial strategy for protecting a main domain's reputation. While a subdomain's negative reputation can sometimes impact the main domain, segmentation of different email streams (transactional, promotional, bulk, and even internal communications) allows for better management and tracking. By separating email types, it reduces the risk of deliverability issues from one stream affecting others. The use of subdomains facilitates granular reputation management, provides a cost-effective alternative to dedicated IPs, and enables DKIM configuration for authentication, further enhancing deliverability. Proper planning and execution are critical to realizing the full benefits of subdomain segmentation. Isolating brand reputation helps ensure marketing blasts don't impact crucial transactional email delivery.

Key findings

  • Reputation Isolation: Subdomains effectively isolate brand reputation, preventing marketing issues from negatively impacting transactional email delivery.
  • Granular Management: Using subdomains allows for finer control over email sending reputation, improving deliverability.
  • Authentication Benefits: DKIM configuration on subdomains enhances deliverability and authenticates email streams.
  • Segmented Control: Subdomains enable separate tracking and management of email types, minimizing risk to the primary domain.
  • Cost Effective: Subdomains provide a cost-effective alternative to dedicated IPs for reputation management.

Key considerations

  • Potential Reputation Impact: A subdomain's negative reputation can potentially affect the main domain, requiring ongoing monitoring.
  • Not Always Mandatory: For senders with strong opt-in practices, the benefit of subdomains may be marginal.
  • Volume Dependent: The advantages of subdomain segmentation are more pronounced with higher email volumes.
  • Strategy Execution: Proper planning and execution are critical to realizing the full benefits of subdomain segmentation.
  • Careful Set-Up Required: Authentication (DKIM) requires proper implementation on each subdomain to achieve maximum deliverability gains.

What email marketers say
11Marketer opinions

The use of subdomains for separating transactional and promotional emails is a common strategy to protect the main domain's reputation. While some sources suggest that a subdomain's reputation can still impact the main domain, the overall consensus indicates that subdomains provide a degree of isolation. This segmentation allows for better tracking and management of email reputation for different email types, minimizing risk to the primary domain. Using subdomains offers a balance between control and cost-effectiveness, especially for those not ready to invest in dedicated IPs. A well-defined subdomain strategy is essential for deliverability, particularly for segmenting transactional, marketing, and bulk emails. Best practices include using distinct subdomains (e.g., transactional.yourdomain.com, marketing.yourdomain.com) and considering segmentation for internal communications as well. The primary advantage is the ability to contain deliverability issues, limiting the impact of spam complaints on the core domain and other subdomains. Additionally, proper setup and management are crucial to realize the benefits of subdomain segmentation effectively.

Key opinions

  • Reputation Isolation: Subdomains provide a level of isolation, so issues with one subdomain are less likely to affect the entire domain's reputation.
  • Segmentation Benefits: Using subdomains allows for better segmentation of email sending, improving tracking and management of reputation for different email types.
  • Cost-Effectiveness: Subdomains offer a balance between control and cost-effectiveness compared to dedicated IPs.
  • Containment of Issues: Subdomains can contain deliverability issues, limiting the impact of spam complaints on the core domain and other subdomains.

Key considerations

  • Reputation Impact: A subdomain's reputation can potentially impact the parent domain, though the impact is typically less severe than if all emails were sent from the main domain.
  • Volume Requirements: For sufficient volume, segmenting mail on 5321/5322/dkim can help, but it's difficult to know how each MBP handles domain reputation.
  • Strategy Definition: A well-defined subdomain strategy is essential for deliverability, and proper setup and management are crucial for realizing the benefits effectively.
  • Segmentation scope: Consider segmenting not only transactional and promotional emails but also internal communications to avoid crossover issues.
Marketer view

Email marketer from SendGrid mentions that subdomains allow for better segmentation of your email sending. By using different subdomains for transactional and promotional emails, you can better track and manage the reputation of each type of email, minimizing the risk to your primary domain.

November 2022 - SendGrid
Marketer view

Email marketer from Reddit shares that the key advantage of using subdomains lies in their ability to contain deliverability issues. If one subdomain is impacted by spam complaints, it will have a limited impact on your core domain and other subdomains.

August 2022 - Reddit
Marketer view

Email marketer from Digital Marketing Blog explains that using subdomains provides a safety net. If one subdomain's emails are flagged as spam, it’s less likely to impact the deliverability of emails sent from other subdomains or the primary domain.

June 2024 - Digital Marketing Blog
Marketer view

Marketer from Email Geeks suggests that with sufficient volume, segmenting mail on 5321/5322/dkim can help, but it's difficult to know how each MBP handles domain reputation, and if you're worried about one stream going awry, try to make them seem distinct.

April 2021 - Email Geeks
Marketer view

Email marketer from Email Marketing Forum responds that setting up subdomains for different email types is crucial. They advise using 'transactional.yourdomain.com' and 'marketing.yourdomain.com' to clearly separate traffic and manage sender reputation effectively.

August 2023 - Email Marketing Forum
Marketer view

Email marketer from Quora mentions that while dedicated IPs offer reputation control, subdomains offer a good balance between control and cost-effectiveness. They suggest using subdomains to segment email types, especially if you're not ready to invest in multiple dedicated IPs.

January 2022 - Quora
Marketer view

Email marketer from Reddit shares that subdomains are advantageous because if one subdomain gets a bad reputation, it doesn't necessarily affect your entire domain. This provides a level of isolation and protection for important transactional emails.

December 2022 - Reddit
Marketer view

Email marketer from Tech Forum responds that best practice is to use separate subdomains not only for transactional and promotional emails, but also for internal communications, helping to avoid any crossover issues that could damage overall sender reputation.

September 2022 - Tech Forum
Marketer view

Email marketer from Mailjet shares that using subdomains for different email types (transactional vs. marketing) allows you to segment your sending reputation. If your marketing emails encounter issues, it is less likely to affect the deliverability of your critical transactional emails.

April 2021 - Mailjet
Marketer view

Email marketer from Pepipost shares that a well-defined subdomain strategy is essential for email deliverability. They advocate for separating transactional, marketing, and bulk emails onto distinct subdomains to protect the main domain's reputation and improve overall email performance.

February 2023 - Pepipost
Marketer view

Marketer from Email Geeks explains that if one subdomain sends spam, the parent domain and potentially other subdomains' reputation could be impacted, as reputation systems are sophisticated.

October 2021 - Email Geeks

What the experts say
5Expert opinions

Experts generally agree that using subdomains is a good practice for managing email reputation, particularly for isolating different email streams such as transactional and promotional. Setting up authentication like DKIM with subdomains allows for reputation segregation without changing the user experience. While not always considered a 'best practice' in the 5322.from, using subdomains won't typically hurt deliverability, especially for opted-in recipients. For significant growth, fully separating subdomains with their own DKIM is recommended. This segmentation protects the core domain and allows granular management of sender reputation by using d= for DKIM signatures and separating emails by ESP.

Key opinions

  • Isolation of Reputation: Subdomains effectively isolate brand reputation, preventing marketing issues from impacting transactional email delivery.
  • Granular Management: Subdomains allow for more granular management of email sending reputation and improved deliverability.
  • Authentication Options: Authentication methods like DKIM can be set up with subdomains without changing what the user sees.
  • Growth Recommendation: For significant growth, fully separating subdomains with their own DKIM is recommended.

Key considerations

  • Not Always a Best Practice: Using subdomains is not universally considered a 'best practice,' though it generally won't hurt deliverability.
  • Opt-In Importance: For opted-in recipients, the chances of domain-based reputation problems are slim, regardless of subdomain use.
  • DKIM Segmentation: Using d= for DKIM signatures and separating emails by ESP can further enhance subdomain segmentation.
  • Fully Authenticated Subdomains: Ensuring subdomains are fully authenticated (with their own DKIM) is essential for maximum benefit.
Expert view

Expert from Spam Resource explains that using subdomains effectively isolates your brand reputation. This isolation helps ensure that problems with marketing blasts will not impact delivery of transactional email. The article advocates using subdomains to separate different sending streams and protect the core domain.

August 2022 - Spam Resource
Expert view

Expert from Word to the Wise, Laura Atkins, addresses that subdomains are a good idea to segregate streams of mail for reputation purposes, by segmenting using d= for DKIM signatures, different ESPs, etc. This allows for more granular management of your email sending reputation and improved deliverability.

March 2021 - Word to the Wise
Expert view

Expert from Email Geeks shares that you can set up authentication with subdomains (DKIM signature with d=promotions.company.com or d=transactions.company.com) without changing what the user sees, giving you some benefits of subdomains without extra headache.

June 2024 - Email Geeks
Expert view

Expert from Email Geeks recommends fully separating subdomains for from addresses when growing significantly, setting up a fully authenticated subdomain (with its own DKIM) for each subdomain.

April 2021 - Email Geeks
Expert view

Expert from Email Geeks expresses that it's not necessarily a best practice to use subdomains in the 5322.from, but it's a fine practice and won't hurt you. Also, if you’re sending wanted mail to folks who’ve opted in to your message, then the chances of you having domain based reputation problems is slim.

February 2025 - Email Geeks

What the documentation says
4Technical articles

Email deliverability documentation generally supports the use of subdomains for managing and protecting sender reputation. Google Workspace Admin Help recommends setting up separate subdomains to isolate reputation issues and manage email traffic. SparkPost suggests isolating promotional emails to protect the primary domain from potential deliverability problems. While Microsoft's documentation doesn't explicitly advocate for subdomains, it emphasizes segmenting email streams and monitoring reputation, which subdomains can facilitate. DKIM can be configured on subdomains to improve deliverability and authenticate emails, as noted in RFC documentation.

Key findings

  • Reputation Isolation: Subdomains can help isolate reputation issues, preventing problems with one email stream from affecting others.
  • Email Stream Separation: Subdomains are a common practice for separating email streams, particularly promotional and transactional emails.
  • Authentication Support: DKIM can be configured on subdomains to improve deliverability and authenticate emails.
  • Facilitates Segmentation: Subdomains facilitate segmenting email streams, which is emphasized as important for maintaining a good sender reputation.

Key considerations

  • Explicit Advocacy: Not all documentation explicitly advocates for subdomains, but they generally support the underlying principles of segmentation and reputation management.
  • Configuration Required: Setting up separate subdomains for different email types and configuring authentication methods requires careful planning and execution.
  • Monitoring Needed: While subdomains help, it's still crucial to monitor the reputation of each subdomain to ensure optimal deliverability.
Technical article

Documentation from Google Workspace Admin Help explains that using subdomains can help organize and manage email traffic, potentially isolating reputation issues. They recommend setting up separate subdomains for different types of emails to protect the main domain's reputation.

May 2021 - Google Workspace Admin Help
Technical article

Documentation from Microsoft explains that maintaining a good sender reputation is crucial for email deliverability. While they don't explicitly advocate for subdomains, the document emphasizes the importance of segmenting email streams and monitoring reputation, which can be facilitated by using subdomains.

August 2022 - Microsoft
Technical article

Documentation from RFC explains that DKIM (DomainKeys Identified Mail) can be configured on subdomains, allowing you to authenticate emails sent from those subdomains. This helps improve deliverability and protect your domain's reputation.

March 2021 - RFC
Technical article

Documentation from SparkPost explains that using subdomains is a common practice to separate email streams. They suggest isolating promotional emails on a separate subdomain to protect the primary domain's reputation from potential deliverability issues caused by marketing campaigns.

September 2022 - SparkPost


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