Summary
Pointing a single subdomain to multiple email service providers (ESPs) is generally discouraged due to complexities and potential conflicts with email authentication protocols (SPF, DKIM, DMARC). While technically feasible in some limited scenarios (e.g., using separate subdomains or carefully managing sending domains), it introduces significant challenges in maintaining email deliverability and domain reputation. SPF record limitations, DKIM key management, and DMARC compliance become more complex, making it best practice to dedicate subdomains to individual ESPs. Using the same subdomain as a bounce domain is not possible. Authentication with SPF and DKIM is essential to help ensure deliverability.
Key findings
- SPF Limitations: SPF records are tied to specific domains or subdomains, making it difficult to use the same subdomain for multiple ESPs without creating conflicts due to DNS lookup limits.
- DKIM Complexity: While DKIM can be configured for multiple ESPs, each requires separate keys and DNS configurations, increasing complexity.
- DMARC Challenges: DMARC compliance is complicated when using multiple ESPs on the same domain due to alignment requirements with SPF, DKIM, and the From address.
- Deliverability Risks: Improper configuration with multiple ESPs can negatively impact email deliverability, leading to emails being marked as spam or blocked.
- Bounce Domain Restriction: The same subdomain cannot be used as the bounce domain for multiple ESPs.
- Authentication is Key: Setting up SPF and DKIM is essential for improving deliverability.
Key considerations
- Separate Subdomains: Use separate subdomains for each ESP (e.g., mail1.domain.com, mail2.domain.com) to simplify authentication and avoid conflicts.
- Dedicated IPs: Consider using dedicated IP addresses for each ESP to isolate reputation and improve control.
- SPF Management: Carefully manage SPF records, including 'include' statements, to avoid exceeding DNS lookup limits.
- Monitor Reputation: Regularly monitor domain reputation to detect and address deliverability issues.
- Authentication: Authenticate email to help ensure deliverability.
What email marketers say
11 marketer opinions
The ability to point a single subdomain to multiple email service providers (ESPs) is technically complex and generally not recommended due to potential conflicts with email authentication protocols like SPF, DKIM, and DMARC. While using different subdomains for each ESP is a viable alternative, using the same subdomain as the bounce domain is not possible. Proper configuration, including dedicated IP addresses and careful DNS management, is crucial for maintaining deliverability and avoiding reputation issues.
Key opinions
- Technical Complexity: Pointing one subdomain to multiple ESPs is technically challenging due to email authentication requirements.
- SPF Conflicts: Using the same subdomain with multiple ESPs can lead to SPF record conflicts and exceed DNS lookup limits.
- DKIM Requirements: Each ESP requires separate DKIM keys and proper DNS configuration for verification.
- DMARC Complications: DMARC compliance is complicated when using multiple ESPs on the same domain due to alignment issues.
- Bounce Domain Limitation: Using the same domain/subdomain as the bounce domain is not possible.
- Deliverability Impact: Improper configuration can negatively impact email deliverability and domain reputation.
Key considerations
- Use Separate Subdomains: Consider using different subdomains for each ESP (e.g., mail1.domain.com, mail2.domain.com) to avoid conflicts.
- Dedicated IP Addresses: Utilize dedicated IP addresses for each ESP to prevent shared reputation issues.
- Email Authentication: Ensure proper SPF, DKIM, and DMARC configuration for each ESP to authenticate your emails.
- Domain Reputation: Monitor domain reputation to ensure emails are delivered to the inbox and not filtered to spam.
- Bounce Domain: Each ESP needs it's own bounce domain.
Marketer view
Email marketer from EmailOctopus explains that by authenticating your domain, you're telling mailbox providers that you've given EmailOctopus permission to send emails on your behalf. You will need to set up SPF and DKIM records.
9 Jul 2021 - EmailOctopus
Marketer view
Email marketer from Reddit suggests its generally not best practice to use the same subdomain for multiple ESPs. He recommends using separate subdomains as it simplifies email authentication configuration and management and improves overall email deliverability.
1 Oct 2022 - Reddit
What the experts say
3 expert opinions
Using multiple ESPs with one subdomain is generally discouraged due to potential SPF conflicts and DNS lookup limitations. A common recommendation is to use separate subdomains for each ESP (e.g., mail3.yourcompany.com, mail4.yourcompany.com). Utilizing multiple third-party senders/ESPs can quickly exceed SPF record limits due to include statements, negatively impacting email deliverability.
Key opinions
- SPF Conflicts: Using a single domain with multiple ESPs can lead to SPF conflicts due to DNS lookup limits.
- DNS Lookup Limits: SPF records have a limit on the number of DNS lookups, and multiple ESPs can easily exceed that limit.
- Include Statement Limitations: SPF include statements for third-party senders/ESPs count towards the total DNS lookup limit.
- Alternate Subdomains: Set up different subdomains for each email service provider.
Key considerations
- Separate Subdomains: Consider using separate subdomains for each ESP to avoid SPF conflicts and DNS lookup limitations.
- SPF Record Management: Carefully manage your SPF records and monitor DNS lookup counts.
- Optimize SPF Includes: Review and optimize SPF include statements to stay within DNS lookup limits.
Expert view
Expert from Word to the Wise explains that using a single domain with multiple ESPs can lead to SPF (Sender Policy Framework) conflicts. SPF records have a limit to the number of DNS lookups, and using multiple ESPs could easily exceed that limit, causing deliverability issues.
11 Sep 2023 - Word to the Wise
Expert view
Expert from Spamresource.com explains that you can use include: statements in your SPF record. These 'includes' count towards the total limits. If you’re using multiple third party senders like ESPs, those include: statements can add up quickly.
5 Nov 2022 - Spamresource.com
What the documentation says
5 technical articles
Email authentication protocols such as SPF, DKIM, and DMARC play a crucial role in email deliverability. SPF records, tied to specific domains or subdomains, authorize mail servers to send emails on behalf of that domain, making it difficult to use one subdomain for multiple ESPs without creating conflicts. DKIM can be configured for multiple ESPs, but each requires separate keys and DNS configuration, adding complexity. DMARC relies on SPF and DKIM, and using multiple ESPs on the same domain complicates DMARC compliance. Best practices from Microsoft and Google emphasize authenticating email using SPF or DKIM for improved deliverability.
Key findings
- SPF Limitations: SPF records are tied to specific domains/subdomains, limiting the use of one subdomain for multiple ESPs without careful configuration.
- DKIM Complexity: DKIM can be configured for multiple ESPs but requires separate keys and DNS configuration for each, increasing complexity.
- DMARC Challenges: Using multiple ESPs on the same domain complicates DMARC compliance due to alignment issues between SPF, DKIM, and the From address.
- Authentication Importance: Microsoft and Google recommend authenticating email with SPF or DKIM to improve deliverability.
Key considerations
- Address SPF Conflicts: Carefully configure SPF records to avoid conflicts when using multiple ESPs.
- Manage DKIM Keys: Implement separate DKIM keys and DNS configurations for each ESP.
- Ensure DMARC Compliance: Monitor and manage DMARC compliance when using multiple ESPs to ensure proper email handling.
- Implement Authentication: Set up and maintain SPF and DKIM records.
Technical article
Documentation from DKIM.org explains DKIM (DomainKeys Identified Mail) allows an organization to take responsibility for a message in a way that can be verified by a recipient. While DKIM can be configured with multiple ESPs using selector tags, each ESP requires separate DKIM keys and proper DNS configuration for verification, making a single subdomain setup complex.
4 Dec 2024 - DKIM.org
Technical article
Documentation from RFC Editor outlines the technical specifications for SPF records. It states that SPF records are tied to specific domains or subdomains and define which mail servers are authorized to send emails on behalf of that domain. This inherently limits the ability to use the same subdomain for multiple, independently managed ESPs without careful configuration to avoid SPF record conflicts.
7 Dec 2023 - RFC Editor
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