Summary
Using different hostname subdomains pointing to IPs for email sending is generally acceptable and can offer benefits like improved segmentation and sender reputation management. However, proper configuration is paramount. This includes DNS records (SPF, DKIM, DMARC), PTR records, and DMARC alignment. Subdomains do not inherit the reputation of the parent domain and require independent warm-up and monitoring. A clear strategic reason for using subdomains is crucial, and potential misunderstandings surrounding their implementation should be addressed. The IP address reputation can also affect subdomain deliverability. Multiple domains on a single IP are acceptable due to the existence of shared IP pools.
Key findings
- Acceptable Practice: Using different host name subdomains is acceptable when properly configured.
- Segmentation and Reputation: Subdomains help segment traffic (e.g., transactional vs. marketing) and manage sender reputation.
- No Reputation Inheritance: Subdomains do not inherit the parent domain's reputation and require separate warm-up.
- DNS and Authentication: Properly configuring SPF, DKIM, DMARC, and PTR records is essential for authentication.
- DMARC Alignment: DMARC alignment is crucial; settings may need adjustment.
- IP Reputation Impact: The IP address reputation influences subdomain deliverability.
- Strategic Justification: A clear and justifiable reason for subdomain usage is necessary.
Key considerations
- Warm-up and Monitoring: Warm up new subdomains and monitor their deliverability metrics independently.
- DNS Configuration: Ensure correct DNS delegation and record configuration for each subdomain.
- Strategic Planning: Develop a clear strategy for subdomain use, avoiding misunderstandings.
- IP Reputation Management: Monitor and maintain the IP address's sending reputation.
- DMARC Compliance: Comply with DMARC alignment requirements.
- Purpose: There needs to be a clear objective for creating the subdomains to begin with.
What email marketers say
10 marketer opinions
Using different host name subdomains pointing to IPs can be a valid strategy for email marketing, allowing for segmentation of email traffic and better management of sender reputation. However, it is crucial to properly configure the subdomain, including DNS records (SPF, DKIM, DMARC), and to warm up the subdomain's IP address to build a positive reputation, as subdomains do not inherit the reputation of the parent domain. Monitoring subdomain deliverability metrics separately is also essential.
Key opinions
- Segmentation: Subdomains enable segmentation of email traffic (e.g., transactional vs. marketing), improving organization.
- Reputation Isolation: Subdomains help protect the main domain's reputation by isolating different types of email traffic.
- No Inheritance: Subdomains do not automatically inherit the reputation of the parent domain; each subdomain requires separate warm-up and reputation building.
- Independent Monitoring: Subdomain deliverability metrics should be monitored separately from the parent domain.
- Proper Configuration: Proper DNS record configuration (SPF, DKIM, DMARC) is essential for subdomain deliverability.
Key considerations
- Warm-up Required: New subdomains require a warm-up period to establish a positive sending reputation.
- DNS Configuration: Ensure SPF, DKIM, and DMARC records are correctly configured for each subdomain.
- Reputation Monitoring: Monitor subdomain deliverability metrics (e.g., bounce rates, spam complaints) independently.
- Potential Deliverability Issues: Improper subdomain setup can lead to deliverability problems and emails being marked as spam.
- Strategic Rationale: Have a well articulated strategic reason for implementing subdomains in email sending.
Marketer view
Marketer from Email Geeks explains that using multiple domains on a single IP is acceptable because shared IP pools exist.
13 Jun 2023 - Email Geeks
Marketer view
Email marketer from Reddit advises that using a new subdomain requires a separate warm-up process to build its reputation, even if the main domain has a good reputation. Without proper warm-up, deliverability can be negatively affected. You also have to configure SPF, DKIM, and DMARC.
24 May 2024 - Reddit
What the experts say
5 expert opinions
Using different host name subdomains requires a well-defined strategy and careful consideration. While it can be a good way to protect the primary domain's reputation, particularly when separating transactional and marketing emails, IP address reputation can affect the sending subdomains. Ensuring correct DNS delegation and proper configuration is also crucial for optimal deliverability. Relaxing DMARC alignment requirements may also be necessary when using multiple subdomains in the From header.
Key opinions
- Reputation Protection: Subdomains can protect the primary domain's reputation by segregating email types.
- Strategic Importance: Having a clear and justifiable reason for using subdomains is critical.
- IP Reputation Influence: The reputation of the IP address can affect sending subdomains' deliverability.
- DNS Delegation: Correct DNS delegation and configuration are essential for deliverability.
- DMARC Alignment: DMARC alignment requirements may need adjustment when employing multiple subdomains.
Key considerations
- Reason for Use: Clearly define the purpose and benefits of using subdomains.
- IP Reputation: Monitor and maintain the reputation of the sending IP address.
- DNS Configuration: Verify and properly configure DNS records, including delegation.
- DMARC Settings: Assess and potentially adjust DMARC alignment settings based on subdomain usage.
- Misunderstandings: Ensure any reasons are not born out of misunderstanding of any ESP or someone elses advice.
Expert view
Expert from Email Geeks suggests ensuring DMARC alignment requirements are relaxed when using multiple subdomains in the From header. It is acceptable but you need a good reason to do it.
2 Nov 2021 - Email Geeks
Expert view
Expert from Email Geeks advises having a clear, well-articulated reason for using subdomains in the From: header and re-evaluating the decision if the reason is unclear or based on misunderstandings.
13 Dec 2023 - Email Geeks
What the documentation says
5 technical articles
Using different host name subdomains for email can be acceptable for organizational purposes, provided that DNS records are properly configured. SPF, DKIM, and DMARC records are essential for subdomains to ensure proper authentication and prevent deliverability issues. DMARC alignment is critical, and a missing or incorrect PTR record can negatively impact deliverability.
Key findings
- Organizational Use: Subdomains can be used for organizational purposes in email sending.
- DNS Configuration: Proper DNS configuration is paramount for subdomain deliverability.
- Authentication Standards: SPF, DKIM, and DMARC records are crucial for authenticating subdomains.
- DMARC Alignment: DMARC alignment between the From: header and DKIM/SPF is vital.
- PTR Records: Valid PTR records are necessary for mail servers' IP addresses.
Key considerations
- DNS Setup: Carefully configure SPF, DKIM, and DMARC records for each subdomain.
- DMARC Compliance: Ensure DMARC alignment to avoid deliverability problems.
- PTR Record Verification: Verify that all IP addresses have valid PTR records pointing back to the sending domain.
- Potential Issues: Incorrect subdomain setup can lead to emails being marked as junk or spam.
- RFC Compliance: Adhere to RFC standards for email routing and address interpretation.
Technical article
Documentation from Microsoft warns that incorrect subdomain setup can lead to deliverability issues and emails being marked as junk. It highlights the importance of configuring SPF records to authorize sending from the subdomain.
24 Mar 2024 - Microsoft
Technical article
Documentation from IETF explains the importance of PTR records for mail servers. All IP addresses used to send mail should have a valid PTR record which resolves back to the sending domain. A missing or incorrect PTR record may negatively affect deliverability.
24 Jul 2021 - IETF
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