Should I use separate email subdomains for transactional and promotional emails, and how does engagement affect this?

Key findings

• Reputation Isolation: Using separate subdomains isolates sender reputation, protecting transactional emails from issues affecting promotional emails.
• Improved Deliverability: Segmenting email traffic by subdomain improves overall deliverability rates, particularly for transactional emails.
• Control Over Reputation: Subdomains provide greater control over sender reputation management, allowing for the isolation and resolution of deliverability problems.
• Technical Support: Technical documentation from Google, SparkPost, Microsoft and RFC Editor supports the practice of using subdomains to separate email traffic and isolate sender reputation.

Key considerations

• Infrastructure Sharing: Shared infrastructure, like IP addresses, can cause reputation bleeding between subdomains, potentially negating the benefits of separation.
• Reputation Management Overhead: Creating and maintaining separate subdomains requires additional effort in managing and monitoring their individual reputations.
• Mailbox Provider Variations: It's important to understand how different mailbox providers handle subdomain reputation, as their policies and practices can vary.
• Data Quality Importance: Maintaining high data quality (e.g., validating email addresses) is crucial for overall sender reputation, regardless of subdomain usage.

Key opinions

• Reputation Isolation: Separate subdomains help isolate sender reputation, preventing issues with promotional emails from impacting transactional email deliverability.
• Deliverability Improvement: Segmenting transactional and promotional emails onto different subdomains improves overall deliverability.
• Control Over Reputation: Separating subdomains gives more control over sender reputation, allowing for the isolation and management of deliverability issues.
• Protection of Core Domain: Subdomains protect the core domain's reputation, minimizing the impact of marketing campaign issues.

Key considerations

• Infrastructure Sharing: Shared infrastructure, such as IP addresses, can cause reputation bleeding between subdomains.
• Reputation Management: Creating new subdomains requires managing their individual reputation.
• Data Quality: Addressing data quality (e.g., invalid addresses) is crucial for sender reputation.
• Engagement Balancing: High engagement campaigns can balance out the metrics for lower engagement ones.

Key opinions

• Subdomain for Transactional Emails: Sending transactional emails from a separate subdomain improves sender reputation.
• Separate IP for Transactional Emails: Using a separate sending IP for transactional emails further enhances sender reputation.

Key considerations

• Shared Infrastructure: Shared IP addresses can cause reputation bleeding between subdomains and the main domain.
• Mailbox Provider Handling: Understanding how mailbox providers handle subdomain reputation is crucial for your sending context.

Key findings

• Reputation Isolation: Subdomains allow for isolating the reputation of different email streams.
• Segmented Email Traffic: Subdomains are useful for segmenting different types of email traffic.
• Independent Entities: Subdomains are treated as separate entities from a technical perspective.
• Improved Deliverability: Using subdomains improves deliverability for critical transactional emails by protecting them from negative impacts on promotional emails.

Key considerations