Summary
Experts, marketers, and documentation consistently recommend using subdomains to separate promotional and transactional emails when on a shared IP. This isolates sender reputation, protecting critical transactional emails from deliverability issues potentially caused by promotional campaigns. The approach enables granular control through separate SPF and DKIM configurations, simplifies issue monitoring, and is considered a best practice for maintaining a healthy email infrastructure on shared IPs.
Key findings
- Reputation Isolation: Subdomains isolate sender reputation, preventing deliverability problems with promotional emails from negatively impacting transactional emails.
- Granular Control: Separate SPF and DKIM configurations for each subdomain provide granular control over email authentication.
- Shared IP Benefit: Subdomain separation is particularly beneficial on shared IPs due to the potential impact of other senders' practices.
- Issue Containment: Deliverability issues are contained within a specific subdomain, limiting the overall impact.
- Enhanced Monitoring: Subdomains allow for easier monitoring of deliverability issues.
Key considerations
- SPF/DKIM Configuration: Properly configure SPF and DKIM records for each subdomain to ensure proper authentication.
- Transactional Priority: Prioritize protecting the deliverability of transactional emails due to their importance for user experience.
- Clear Segmentation: Plan a clear subdomain structure (e.g., trans.domain.com, promo.domain.com) to effectively manage different email streams.
- Shared IP Awareness: Be aware of the sending practices of other users on the shared IP and proactively implement subdomain separation for protection.
What email marketers say
11 marketer opinions
The consensus is that using subdomains to separate promotional and transactional emails on a shared IP is highly recommended. This practice isolates sender reputation, preventing deliverability issues with promotional emails from negatively impacting the delivery of critical transactional emails. Subdomain separation also enables individual monitoring of email streams for better issue detection and resolution.
Key opinions
- Reputation Isolation: Subdomains isolate sender reputation, protecting transactional emails from promotional email deliverability issues.
- Deliverability Improvement: Separating email types improves overall deliverability on shared IPs.
- Issue Containment: Deliverability problems are contained to specific subdomains, limiting impact.
- Monitoring: Individual monitoring of subdomains allows for quicker detection and resolution of deliverability issues.
Key considerations
- Shared IP Impact: Using subdomains is particularly important when on a shared IP due to the potential for negative impact from other senders.
- Transactional Importance: Prioritize the deliverability of transactional emails due to their critical role in user experience.
- Sender Reputation: Segmenting email traffic helps protect your sender reputation.
Marketer view
Email marketer from Litmus responds that it's crucial to separate email streams using subdomains when on a shared IP. This approach helps to manage sender reputation and ensures that transactional emails, which are vital for user experience, aren't affected by any deliverability issues with promotional emails.
23 Jun 2023 - Litmus
Marketer view
Email marketer from GMass explains that employing subdomains can help improve deliverability on shared IPs. By separating promotional and transactional emails, you prevent the negative reputation from promotional emails affecting transactional emails. If there are any deliverability problems, they stay isolated to a smaller subdomain.
11 Oct 2021 - GMass
What the experts say
3 expert opinions
Experts generally agree that using subdomains to separate promotional and transactional emails on a shared IP is a best practice. This helps isolate reputation issues stemming from potentially problematic promotional campaigns, protecting the deliverability of critical transactional emails. The use of subdomains also allows for better management and segregation of different email streams, especially vital given the impact of other senders on a shared IP address.
Key opinions
- Reputation Isolation: Subdomains effectively isolate reputation issues between promotional and transactional emails.
- Shared IP Mitigation: Subdomains mitigate the risk of poor sending practices from other users on shared IPs affecting your transactional email delivery.
- DKIM Subdomain Usage: Using subdomains within the DKIM signature (d=) is recommended to manage email domain reputation.
Key considerations
- Shared IP Vulnerability: Shared IPs are vulnerable to the sending practices of other users, making subdomain separation crucial.
- Strategic Subdomain Use: Consider using separate subdomains for promotional, transactional, and corporate emails for clear segregation.
- Deliverability Protection: Prioritize protecting the deliverability of transactional emails due to their importance.
Expert view
Expert from Word to the Wise, Laura Atkins, responds that when using a shared IP, it's beneficial to separate different mail streams via subdomains. Since others are using the same IP, their sending practices can impact your deliverability. By segregating promotional and transactional emails, you mitigate the risk of poor promotional mail practices affecting your transactional email delivery. It mentions that reputation is per domain, and subdomains can help manage this.
1 Dec 2022 - Word to the Wise
Expert view
Expert from Email Geeks explains using a subdomain for the d= of the DKIM signature is a good practice, especially if promotional emails might cause deliverability problems. They suggest using separate subdomains for transactional (e.g., trans.whatever) and promotional emails (e.g., promo.whatever), reserving the root domain for corporate mail. This is Laura's preferred way of managing email domains.
1 Oct 2023 - Email Geeks
What the documentation says
5 technical articles
Technical documentation consistently recommends using subdomains to separate promotional and transactional emails, especially on shared IPs. This approach enables distinct SPF and DKIM configurations for each subdomain, providing granular control over email authentication and sender reputation. Isolating email types in this manner helps protect the deliverability of critical transactional emails by preventing issues with promotional sends from negatively affecting the main domain.
Key findings
- Authentication Flexibility: Subdomains allow for configuring separate SPF and DKIM records for different email streams.
- Reputation Protection: Separating email types protects the sender reputation of transactional emails.
- Granular Control: Using subdomains provides granular control over email authentication and deliverability strategies.
- Infrastructure Best Practice: Subdomain separation is part of a well-structured email infrastructure.
Key considerations
- Shared IP Implications: Separate configuration is more important when using a shared IP due to reputation risks.
- SPF and DKIM Setup: Properly configure SPF and DKIM records for each subdomain.
- Transactional Email Priority: Prioritize protecting the deliverability of transactional emails.
Technical article
Documentation from RFC states DKIM signatures can be applied using different subdomains in the 'd=' tag. This practice allows for granular control over email authentication and helps to isolate the reputation of different email streams, which is especially useful with shared IPs.
6 Oct 2023 - RFC 6376
Technical article
Documentation from SparkPost shares using subdomains for different email streams (transactional, marketing) allows you to configure separate sender authentication (SPF, DKIM) for each. This level of control is beneficial when on shared IPs, as it allows you to fine-tune your deliverability strategy for each type of email.
30 Oct 2021 - SparkPost
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