Summary
Pointing a single subdomain to multiple email service providers (ESPs) simultaneously for all email functions is generally not straightforward or fully possible. While you can often use the same subdomain as the "From" address (sending domain) across different ESPs, the underlying infrastructure, particularly the "Return-Path" or bounce domain, typically requires a unique, dedicated setup for each ESP. This distinction is crucial for proper email authentication and deliverability. It's often recommended to use separate subdomains for each ESP to avoid complex DNS conflicts and ensure optimal inbox placement.
Key findings
- Bounce domain limitation: The return-path (bounce) domain, specified in the envelope FROM address, can generally only point to one ESP at a time. This is because MX records (Mail eXchanger records) direct incoming mail (including bounces) for that specific domain or subdomain to a single server.
- Sending domain flexibility: It is often possible to use the same subdomain for your "From" address across multiple ESPs, provided each ESP correctly signs the email with DKIM using that subdomain.
- DNS records: DNS records, such as CNAMEs and MX records, are foundational to how subdomains direct traffic, including email. Each CNAME record typically points a specific hostname to a single canonical name (another domain or hostname), making it difficult to split control for the same record across multiple entities simultaneously.
- Authentication impact: Proper email authentication (SPF, DKIM, DMARC) is essential for deliverability. While SPF is tied to the return-path domain, DKIM can be set up for the sending domain. Mismatched or incorrectly configured records due to multiple ESPs attempting to control the same subdomain can lead to authentication failures and reduced inbox placement.
Key considerations
- Clarity in terminology: Distinguishing between the visible "From" address (sending domain) and the technical "Return-Path" address (bounce domain) is vital to understand the feasibility of pointing a subdomain to multiple ESPs.
- Separate subdomains: For simplicity and robust deliverability, it's generally best practice to use a unique subdomain for each ESP you use for sending. This ensures clear delegation of DNS control and avoids potential conflicts.
- Deliverability impact: Incorrectly configuring DNS records across multiple ESPs for a single subdomain can lead to email deliverability issues, including emails landing in spam or being rejected. Consistent authentication is key.
- SPF record complexity: If multiple ESPs need to send from the same bounce domain, their SPF mechanisms (e.g., include: statements) would need to be combined into a single SPF record without exceeding the 10-DNS lookup limit. This is often impractical or impossible.
What email marketers say
Email marketers often face challenges and confusion when attempting to use a single subdomain with multiple email service providers. Their experiences highlight common misconceptions and the practical difficulties of managing DNS records for such a setup. Many initially assume it's entirely impossible due to the nature of how domains typically point to single services.
Key opinions
- Initial impossibility: Many marketers initially believe it is not possible to point a single subdomain to two different email systems simultaneously.
- Analogy for understanding: The situation is often compared to trying to make a single phone number ring at two different physical locations, or registering one address for two separate entities.
- Recommendation for separate subdomains: A common practical solution suggested is to simply set up a distinct subdomain for each email service provider.
- Ambiguity of terms: There can be confusion around what exactly 'pointing to' means in the client's context, whether it refers to the bounce domain, sending domain, or SPF records.
Key considerations
- Client communication: Marketers need to clearly explain the technical limitations and recommend alternative strategies to clients who request such a setup.
- DNS management: Understanding how DNS records like CNAMEs and MX records function is crucial to troubleshoot and implement solutions for multiple ESPs.
- Deliverability risk: Attempting to force a single subdomain for all purposes across multiple ESPs can lead to deliverability issues and blocklisting due to misconfigured or conflicting DNS entries.
- Domain reputation: Using distinct subdomains can help isolate reputation, meaning issues with one sending stream are less likely to affect others originating from your primary domain or different subdomains. SendLayer advises using subdomains to protect domain reputation.
Marketer view
Marketer from Email Geeks asks if anyone has seen a subdomain pointed to two different systems, suggesting it feels impossible like a phone ringing at two houses.
Marketer view
Marketer from Email Geeks states definitively that pointing a single subdomain to two different systems is not possible.
What the experts say
Email deliverability experts provide nuanced perspectives on using a single subdomain for multiple email service providers. They delve into the technical distinctions between different types of email domains and how authentication protocols like DKIM enable some flexibility, while other aspects remain strictly one-to-one. A recurring theme is the need for clearer, standardized terminology.
Key opinions
- Conditional possibility: It is possible to use the same subdomain for multiple ESPs, but only for the "sending domain" (the From address), not the bounce domain (Return-Path).
- DKIM's role: DKIM (DomainKeys Identified Mail) is specifically designed to allow the same sending domain to be used with multiple ESPs, as it involves a cryptographic signature rather than direct DNS delegation of the mail stream.
- Terminology challenges: The lack of consistent terminology across ESPs for different email domains creates significant confusion and difficulty in discussing and configuring multi-ESP setups.
- Need for clarification: Experts advocate for clear definitions and visual aids to help users understand which specific domain or address is being referred to in technical discussions.
Key considerations
- SPF limitations: While DKIM offers flexibility, SPF (Sender Policy Framework) still requires careful management. If a subdomain is used as the Return-Path, its SPF record must include all authorized senders from different ESPs, potentially hitting the 10-DNS lookup limit. SpamResource often discusses the intricacies of SPF records.
- DMARC alignment: Implementing DMARC with multiple ESPs for the same domain or subdomain requires careful configuration to ensure both SPF and DKIM align with the "From" domain. Proper DMARC setup is paramount.
- Reputation management: Using separate subdomains for different email streams (e.g., transactional, marketing) can help isolate sender reputation, preventing a problem with one stream from affecting others. WordToTheWise often advocates for this strategic separation.
- Glossary development: The community recognizes the value of a standardized glossary to define terms like "sending domain," "bounce domain," "Return-Path," and "MAIL FROM" consistently across the industry.
Expert view
Expert from Email Geeks clarifies that using the same subdomain for multiple ESPs is possible for the 'sending domain' (From address) due to how DKIM is designed, but not for the 'bounce domain' (Return-Path).
Expert view
Expert from Email Geeks suggests creating a comprehensive glossary with visual aids to simplify the understanding of email sending terminology.
What the documentation says
Official documentation from various email service providers and industry resources often clarifies the technical requirements for setting up email sending, including the use of subdomains. This documentation generally supports the idea of subdomains having independent DNS control and emphasizes the importance of proper authentication for each sending entity, whether it's the primary domain or a subdomain.
Key findings
- Independent DNS entries: Subdomains have their own entries in the DNS, allowing them to point to different IP addresses and host separate services, including email sending.
- Reputation protection: Using subdomains for email helps top senders protect their primary domain's reputation by compartmentalizing different email streams.
- Email organization: Many companies are shifting to using multiple subdomains to manage their email communication better, leading to improved organization.
- Unique sending domains: When a sending domain is created, it becomes a unique web address. For this reason, a subdomain can typically only be used once within your DNS to point to a specific ESP's records for return-path purposes.
Key considerations
- Authentication setup: Each subdomain used for sending email must have its own correctly configured SPF and DKIM records, which are then aligned for DMARC.
- Delegation of control: Some DNS providers support subdomain delegation, allowing users to create and manage subdomains for various purposes, including email. This still implies a singular delegation per subdomain.
- Split domain routing: While not directly about sending from one subdomain via multiple ESPs, some documentation mentions "Split Domain Routing" for receiving email, where users within the same domain can receive mail at different ESPs. This is a different scenario from concurrent sending.
Technical article
Documentation from SendLayer blog states that subdomains have independent DNS entries, enabling them to direct to distinct IP addresses and services.
Technical article
Documentation from Mailgun blog provides insights into how email subdomains function with deliverability, emphasizing their role in safeguarding domain reputation.
Related resources
9 resources
Related pages
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