Summary
BIMI's behavior in subdomains is fundamentally governed by DMARC policies. While DMARC policies are inherited from the parent domain, specific DMARC records at the subdomain level are essential for controlling BIMI display. These records can either enforce the parent domain's BIMI, override it, or disable BIMI altogether. Key methods for controlling BIMI include ensuring DMARC compliance, implementing specific DMARC policies (reject/quarantine), utilizing non-functional BIMI records (e.g., `v=BIMI1;`), and aligning the subdomain's DMARC record with the sending domain. Without explicit DMARC configurations, subdomains default to the parent domain's settings, potentially leading to unintended BIMI displays.
Key findings
- DMARC's Role: BIMI relies heavily on valid DMARC policies for proper functioning in subdomains.
- Inheritance and Overriding: Subdomains inherit DMARC policies, but this inheritance can be overridden with subdomain-specific DMARC records.
- Subdomain Specificity: Controlling BIMI on a subdomain requires implementing a DMARC record directly on that subdomain.
- Disabling BIMI: A non-functional BIMI record (v=BIMI1;) can be used to prevent logo display on a subdomain.
- DMARC Compliance: To effectively enable BIMI, subdomains need to be DMARC compliant, often requiring 'reject' or 'quarantine' policies.
Key considerations
- DMARC Configuration: Carefully configure DMARC records on each subdomain to achieve desired BIMI behavior.
- Enforcement Level: Ensure DMARC policies are enforced (beyond 'p=none') for BIMI to function as expected.
- Alignment: Verify that the subdomain's DMARC record is aligned with the sending domain for optimal BIMI performance.
- Hierarchical Understanding: Understand how DMARC policies cascade from parent domains to subdomains to avoid unintended consequences.
- Testing and Validation: Thoroughly test and validate BIMI configurations across various subdomains and email clients.
What email marketers say
7 marketer opinions
BIMI behavior on subdomains is governed by DMARC policies. Subdomains inherit the parent domain's DMARC policy unless specifically overridden with their own DMARC record. To control BIMI display on subdomains, implementing specific DMARC records is necessary. This can be achieved by setting a DMARC policy of 'reject' or 'quarantine' on the subdomain, ensuring DMARC alignment with the sending domain, or using a non-functional BIMI record (e.g., `v=BIMI1;`) to disable the logo. Without a specific DMARC record, the subdomain will inherit the parent domain's BIMI settings.
Key opinions
- DMARC Inheritance: Subdomains inherit the DMARC policy from the parent domain by default.
- Subdomain Override: To control BIMI on a subdomain, you must create a specific DMARC record for that subdomain.
- BIMI Disable: Setting a non-functional BIMI record (v=BIMI1;) on a subdomain can prevent the BIMI logo from displaying.
- DMARC Requirement: Subdomains must have a DMARC policy of 'reject' or 'quarantine' for BIMI to function correctly in some cases.
- DMARC Alignment: Valid DMARC alignment on the subdomain is crucial for BIMI to work as intended.
Key considerations
- DMARC Configuration: Properly configure DMARC records on subdomains to manage BIMI display effectively.
- Granular Control: Implement specific DMARC policies for each subdomain to achieve granular control over BIMI branding.
- Subdomain Strategy: Consider your subdomain strategy and how BIMI aligns with each subdomain's purpose.
- Testing: Thoroughly test BIMI implementation across different subdomains and email clients to ensure consistent branding.
Marketer view
Email marketer from Mailhardener.com explains the hierarchical nature of DMARC and its effect on BIMI. Subdomains inherit the DMARC policy of the main domain unless overridden. Therefore, BIMI's effect on subdomains is tied to the DMARC policy in place. To disable BIMI on subdomains, setting a specific DMARC record is necessary.
29 Jan 2025 - Mailhardener.com
Marketer view
Email marketer from EmailToolTester.com explains that subdomains need a DMARC policy of 'reject' or 'quarantine' for BIMI to work correctly. If a subdomain uses 'none' or lacks a DMARC record, BIMI may not display.
27 Jun 2022 - EmailToolTester.com
What the experts say
3 expert opinions
Controlling BIMI display on subdomains hinges on properly configured DMARC records. While DMARC policies are inherited, subdomains require their own specific DMARC records to manage BIMI independently from the parent domain. To effectively manage BIMI display and override parent domain settings, it's essential to ensure DMARC compliance and enforcement on each subdomain.
Key opinions
- DMARC Enforcement: BIMI requires DMARC compliance at the subdomain level, implying settings beyond just 'p=reject; sp=none'.
- DMARC Inheritance & Override: While DMARC policies are inherited, controlling BIMI necessitates specific DMARC records on each subdomain.
- Subdomain DMARC Requirement: To prevent a subdomain from using the top-level domain's BIMI, a DMARC record must exist on each subdomain.
Key considerations
- Subdomain Compliance: Ensure each subdomain is DMARC compliant to fully leverage BIMI.
- Specific DMARC Records: Implement specific DMARC records for each subdomain where BIMI needs to be managed separately.
- Override Strategy: Plan a strategy for overriding inherited DMARC policies on subdomains where necessary.
Expert view
Expert from Spam Resource explains that while DMARC policies are inherited by subdomains, controlling BIMI display requires specific DMARC records for each subdomain. A subdomain without a DMARC record will inherit the parent's policy, but to disable BIMI, the subdomain must have its own DMARC record.
12 Sep 2021 - Spam Resource
Expert view
Expert from Word to the Wise details how to manage BIMI in subdomains. Because BIMI relies on the DMARC policy to function correctly, to prevent a subdomain from using the top level domain's BIMI, a DMARC record must exist on each subdomain.
10 Dec 2023 - Word to the Wise
What the documentation says
3 technical articles
BIMI's behavior on subdomains is intrinsically linked to DMARC policies. DMARC policies are inherited by subdomains, and to manage BIMI at the subdomain level, specific DMARC records need to be implemented. The presence and configuration of these subdomain DMARC records determine whether the top-level BIMI record influences the subdomain's branding.
Key findings
- DMARC Dependency: BIMI relies on a valid DMARC policy to function, both at the top level and subdomain level.
- DMARC Inheritance: Subdomains inherit DMARC policies from the parent domain.
- Subdomain Control: Specific DMARC records are necessary at the subdomain level to control BIMI display.
Key considerations
- DMARC Validation: Ensure DMARC policies at the subdomain level pass validation for BIMI to function.
- Policy Configuration: Properly configure DMARC records to dictate whether BIMI applies to a given subdomain.
- Hierarchical Management: Understand the hierarchical nature of DMARC policies when managing BIMI across different subdomains.
Technical article
Documentation from dmarc.org details how DMARC policies are inherited by subdomains. To control BIMI at the subdomain level, specific DMARC records need to be in place for the subdomain. If the subdomain has its own DMARC policy, it will dictate whether BIMI applies.
7 Jul 2023 - dmarc.org
Technical article
Documentation from Entrust.com clarifies that BIMI relies on a valid DMARC policy. Subdomains inherit DMARC policies, influencing BIMI display. Properly configured DMARC records at the subdomain level are necessary for BIMI to function correctly.
19 Feb 2024 - Entrust.com
Do DMARC and BIMI require p=reject to be present on the organizational domain?
Do subdomains need their own DMARC records if the main domain has one?
Does a parent domain need BIMI for subdomain BIMI to work?
Does BIMI require DMARC at the organizational level, and can it be implemented only at the subdomain level?
How do DMARC policies and RUA/RUF settings inherit or override each other between a domain and its subdomains?
How do I implement BIMI for multiple brands with subdomains?
How do I implement DMARC with BIMI on multiple subdomains?
How do I set up DMARC records for subdomains?
How to apply BIMI to a specific subdomain instead of the entire domain?
