The question of whether Brand Indicators for Message Identification (BIMI) introduces a new header to emails is a common one. While the core BIMI record itself is a DNS TXT record, it often works in conjunction with a specific email header to achieve its intended function of displaying your brand logo in supporting inboxes.
The short answer is yes, BIMI can involve an additional email header. This header is known as the BIMI-Selector header. Its role is to inform the receiving email server which specific BIMI record to look for when your domain has multiple brand logos or is using a non-default selector.
Understanding this header is crucial for proper BIMI implementation, especially for organizations that manage multiple brands or use different logos across various sending contexts. While not always strictly required, it provides flexibility and control over how your brand's visual identity is presented.
Understanding the BIMI-Selector header
The BIMI-Selector header explained
The BIMI-Selector header is an optional, but often recommended, addition to your email's metadata. It serves a specific purpose in the BIMI authentication process. When you publish a BIMI record in your DNS, it typically resides at a subdomain like default._bimi.yourdomain.com. However, if you want to use a different selector name to support multiple logos or differentiate campaigns, you'll need this header.
When an email is sent, and a BIMI-capable email client (like Gmail or Yahoo Mail) receives it, the client first checks for the BIMI-Selector header. If present, it instructs the client to look for a BIMI DNS record at selectorname._bimi.yourdomain.com, where selectorname is specified in the header. If the header is absent, the client defaults to checking for default._bimi.yourdomain.com.
Example BIMI-Selector header
BIMI-Selector: v=BIMI1; s=marketing;
In this example, s=marketing indicates that the receiver should look for a BIMI record using the selector 'marketing', thus marketing._bimi.yourdomain.com. This flexibility allows you to display different logos based on the context of the email, such as transactional emails versus marketing newsletters. You can learn more about this on the official BIMI Group website.
Using default BIMI selector
When you use the default BIMI selector, default, you typically do not need to include the BIMI-Selector header in your emails. The receiving email client will automatically look for the default._bimi DNS record.
Simpler setup: Less configuration overhead for a single logo.
Standard behavior: Relies on the widely recognized 'default' selector.
Using custom BIMI selectors
If you define a custom selector, such as 'campaigns' or 'support', you must include the BIMI-Selector header in your emails. This header directs the recipient's mail server to the correct BIMI record for that specific email.
Greater flexibility: Allows for multiple logos or regional branding variations.
Targeted display: You can choose which logo appears based on email content.
The relationship between BIMI DNS records and email headers
How BIMI records interact with headers
The BIMI standard itself is primarily based on a DNS TXT record. This record contains the location of your Verified Mark Certificate (VMC) and the URL of your brand's SVG logo file. When an email server receives an email, it performs several checks to determine if a BIMI logo should be displayed. These checks include DMARC authentication, and potentially looking for the BIMI-Selector header.
It is essential to have a robust DMARC implementation with a policy of 'quarantine' or 'reject' for BIMI to work. This foundational security ensures that your domain is protected against unauthorized use, preventing bad actors from displaying fake logos. Our DMARC monitoring platform can help you reach enforcement quickly and efficiently.
The BIMI-Selector header, when present, acts as a signpost, directing the receiving mail server to the exact DNS record where your BIMI information is stored. Without it, or if it points to a non-existent record, the BIMI logo may not appear, even if you have a valid DNS entry. For more on the requirements and implementation steps for BIMI, check out our detailed guide.
Ensuring BIMI compliance and logo display
Importance of proper implementation
Implementing BIMI correctly, including the thoughtful use of the BIMI-Selector header, is key to leveraging its benefits. A misconfigured header or an incorrect DNS entry can prevent your logo from being displayed, diminishing the positive impact on brand recognition and trust. Remember that BIMI does not work without a DMARC record, making DMARC the critical first step.
Key considerations for BIMI and headers
DMARC enforcement: A DMARC policy of p=quarantine or p=reject is required.
SPF and DKIM alignment: Your email authentication protocols must align correctly with your domain, as BIMI builds upon these standards. Learn more with our simple guide to DMARC, SPF, and DKIM.
VMC requirement: For most major mailbox providers, a Verified Mark Certificate is needed.
Consistent logo: Ensure your logo is trademarked and consistently presented across all channels.
Regular monitoring of your DMARC reports is highly recommended to ensure that your email authentication is consistently passing, which is a prerequisite for BIMI to function. Tools like Suped provide detailed insights and AI-powered recommendations to help you maintain optimal email deliverability and BIMI compliance. Our platform brings together DMARC, SPF, and DKIM monitoring with blocklist and deliverability insights, offering a unified view of your email health.
Without proper authentication and a correct BIMI setup, your brand logo might not appear in recipients' inboxes, missing out on the opportunity to build trust and improve engagement. Mailhardener explains BIMI headers in more detail.
Summary of BIMI and email headers
Conclusion
In conclusion, while BIMI relies heavily on a DNS TXT record for its core configuration, the BIMI-Selector email header plays a vital role, especially when utilizing custom selectors or managing multiple brand identities. This header allows for dynamic selection of BIMI records, providing flexibility in how your brand's logo is displayed to recipients.
Proper configuration of both your BIMI DNS records and the optional BIMI-Selector header is essential for successful BIMI adoption. This, combined with strong DMARC enforcement, ensures that your authenticated brand logo consistently appears in supporting email clients. This enhances your email security and helps to build recipient trust.
By understanding the interplay between BIMI DNS records and the email header, you can effectively implement BIMI and reap the benefits of increased brand visibility and improved email engagement. Always verify your setup to ensure that your logo shows in Gmail and Yahoo Mail as intended.
Gmail or 
Yahoo Mail) receives it, the client first checks for the BIMI-Selector header. If present, it instructs the client to look for a BIMI DNS record at selectorname._bimi.yourdomain.com, where selectorname is specified in the header. If the header is absent, the client defaults to checking for default._bimi.yourdomain.com.
