Summary
Email marketing experts and official documentation consistently affirm that any subdomain utilized for sending emails must have its own dedicated Sender Policy Framework (SPF) record. This is crucial because SPF records are domain-specific and do not automatically extend from a main domain to its subdomains. Each sending subdomain is treated as a unique entity for authentication, requiring its own distinct SPF record to ensure proper email deliverability, prevent spoofing, and validate authorized sending servers.
Key findings
- Domain Specificity: SPF records are fundamentally domain-specific TXT resource records, meaning they apply only to the precise domain name under which they are published, not broadly across parent domains.
- No Inheritance: A subdomain does not inherit the SPF policy or record from its parent or main domain; each sending subdomain requires its own unique SPF record.
- Direct Lookup: When an email is sent from a subdomain, the SPF check is performed directly on that specific subdomain. DNS resolvers look for an SPF record at the exact sending subdomain, not the root domain.
- Distinct Entities: For email authentication purposes, subdomains are treated as separate and distinct entities from their parent domains, necessitating individual authentication configurations like SPF.
Key considerations
- Proactive Authentication: Go 'overboard' on email authentication for subdomains; comprehensive setup pays dividends by accounting for various server checks and ensuring robust security.
- Deliverability Impact: Failing to establish a dedicated SPF record for a sending subdomain can lead to authentication failures, significantly impacting email deliverability.
- Spoofing Prevention: Proper SPF configuration for each sending subdomain is vital for preventing email spoofing and phishing attempts by unauthorized senders.
- DNS Management: Email marketers and administrators must proactively manage DNS settings for each subdomain used for sending, ensuring a distinct SPF TXT record is created and maintained.
What email marketers say
12 marketer opinions
Regarding email deliverability, the consensus among experts is unequivocal: a subdomain used for sending emails absolutely needs its own unique Sender Policy Framework (SPF) record. This is because SPF authentication operates on a strict domain-specific basis, meaning the record published on your main domain will not automatically cover any subdomains. When an email is sent from a subdomain, mail servers perform a direct DNS lookup for the SPF record specifically on that subdomain, making a dedicated entry vital for proper authentication and successful delivery.
Key opinions
- Subdomain Specificity: SPF records are tied exclusively to the exact domain or subdomain where they are published; they do not apply across parent-child domain relationships.
- No Automatic Inheritance: Unlike some other DNS configurations, SPF records do not automatically extend from a primary domain to its subdomains, requiring individual setup.
- Direct Lookup Requirement: Email authentication systems perform direct DNS queries for the SPF record on the specific sending subdomain, not the root domain.
- Separate Authentication Entity: For email sending and authentication purposes, a subdomain is regarded as a distinct entity from its parent domain, demanding its own authentication configurations.
Key considerations
- Impact on Deliverability: Omitting a dedicated SPF record for a sending subdomain will lead to authentication failures and reduced email deliverability.
- Enhanced Anti-Spoofing: A properly configured SPF record on each sending subdomain is fundamental for preventing email spoofing and validating sender identity.
- Diligent DNS Management: Maintaining accurate and unique SPF records for all sending subdomains is a critical task for email marketers and system administrators.
- Robust Authentication Strategy: Implementing comprehensive authentication, including distinct SPF for subdomains, is a best practice that yields significant long-term benefits for email reputation and successful delivery.
Marketer view
Email marketer from Email Geeks explains that she would typically set up an SPF record for a subdomain used for sending emails, emphasizing going 'overboard' on authentication to account for various server checks and that 'kitting' a domain for authentication pays dividends over time.
6 Aug 2021 - Email Geeks
Marketer view
Email marketer from Email Geeks confirms that a subdomain needs its own SPF record. He clarifies that DNS treats all domains equally, meaning a specific record is needed for an exact match unless a protocol like DMARC specifies otherwise.
26 May 2023 - Email Geeks
What the experts say
2 expert opinions
Leading experts in email deliverability consistently confirm that a subdomain used for sending emails requires its own distinct Sender Policy Framework (SPF) record. This is because SPF policies are strictly tied to specific hostnames, meaning the SPF record of a primary domain does not automatically apply to or cover its subdomains. Therefore, a dedicated SPF entry for each sending subdomain is crucial for accurate email authentication and ensuring messages reach their intended recipients.
Key opinions
- Individual SPF Required: Every subdomain utilized for sending emails necessitates its own distinct SPF record.
- Hostname-Level Application: SPF policies are evaluated at the specific hostname from which an email originates, not inherited from parent domains.
- Absence of Inheritance: An SPF record published for a main domain will not automatically extend its authentication coverage to its subdomains.
- Direct Subdomain Verification: Email recipients' servers perform a direct DNS lookup for the SPF record on the exact sending subdomain, not the root domain.
Key considerations
- Critical for Deliverability: Without a unique SPF record, emails sent from a subdomain are highly likely to fail authentication, leading to poor deliverability.
- Essential for Anti-Spoofing: Proper SPF configuration on subdomains actively helps prevent malicious actors from spoofing your sending identity.
- Careful DNS Administration: Email marketers must undertake meticulous DNS management to ensure each sending subdomain has its own correctly configured SPF TXT record.
Expert view
Expert from Spam Resource explains that if you send mail using a subdomain, that subdomain will need its own SPF record because SPF records are applied to specific hostnames.
28 Nov 2024 - Spam Resource
Expert view
Expert from Word to the Wise explains that if you send email from a subdomain, you will need to publish an SPF record on that specific subdomain.
24 May 2023 - Word to the Wise
What the documentation says
5 technical articles
A subdomain used for email sending requires its own Sender Policy Framework (SPF) record, a consistent recommendation across major email and DNS service providers. This is because SPF authentication operates at the specific domain or hostname level, meaning a main domain's SPF policy does not automatically extend to its subdomains. To ensure proper email authentication and enhance deliverability, an email sent from a subdomain will trigger an SPF check directly on that subdomain, necessitating its dedicated record.
Key findings
- Subdomain Specific SPF: Each subdomain employed for sending email mandates its own individual SPF record.
- No Policy Inheritance: SPF records are not inherited from a parent or root domain; they must be explicitly configured for each subdomain.
- Direct Authentication Lookup: When an email originates from a subdomain, the SPF validation process specifically queries the DNS for that exact subdomain's record.
- Distinct Authentication Entities: From an email authentication standpoint, subdomains are considered separate entities from their primary domains, requiring independent configurations.
Key considerations
- Crucial for Deliverability: Absence of a dedicated SPF record for a sending subdomain can lead to authentication failures, resulting in emails being flagged as spam or rejected.
- Enhanced Security: Properly configured SPF records on subdomains are essential for validating sender identity and safeguarding against email spoofing and phishing attacks.
- Mandatory DNS Management: Administrators must create and maintain distinct SPF TXT records within the DNS settings for every subdomain used in email campaigns.
- Compliance with Standards: Adhering to the principle of individual SPF records for subdomains aligns with established email authentication protocols like RFC 7208.
Technical article
Documentation from RFC 7208 explains that SPF records are TXT resource records specific to a given domain name. If email is sent from a subdomain, the SPF check is performed on that subdomain directly, not the parent domain. Therefore, a subdomain used for sending email needs its own dedicated SPF record, as it does not inherit the parent domain's SPF policy.
10 May 2023 - RFC 7208
Technical article
Documentation from Google Workspace Admin Help states that each domain or subdomain you use to send email needs its own SPF record configured in its DNS settings. This record specifies which mail servers are authorized to send email on behalf of that specific domain or subdomain, ensuring proper authentication and helping to prevent spoofing and phishing.
4 Jul 2021 - Google Workspace Admin Help
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