It's a common and understandable question. Since Brand Indicators for Message Identification (BIMI) works alongside technical standards like DMARC, SPF, and DKIM, it's natural to wonder if it, too, requires adding a special header to your emails. The answer is a bit nuanced, but for the most part, senders do not add a new, dedicated BIMI header to their messages.
Instead, the process relies almost entirely on DNS records that are checked by the recipient's mail server. The outcome of that check is then noted in the email's headers, but not in a new header you create yourself. Let's break down how that works and explore the one exception where a sender can add a BIMI-related header.
How BIMI validation appears in headers
At its core, BIMI is a DNS standard. You, the domain owner, publish a specific TXT record in your DNS. When a mailbox provider that supports BIMI receives your email, it first checks that your message passes DMARC authentication. If it does, the provider then performs a DNS lookup to find your BIMI record. This record tells the provider where to find your brand's logo.
The crucial part is what happens next. The receiving mail server, not the sender, records the result of this BIMI check in an existing header called the Authentication-Results header. This header acts as a scorecard for various authentication checks.
So, alongside the results for SPF and DKIM, you will see a result for BIMI. For example, a passing BIMI check might look like this inside the header: bimi=pass. This information within the headers is exactly what email clients use to decide whether to display your logo, as noted by Kickbox in their analysis of Apple's BIMI support.
The exception: The BIMI-Selector header
While you don't add a primary BIMI header, there is a specific, optional header that senders can use for more advanced cases: the BIMI-Selector header.
This header allows you to specify which of your brand logos should be displayed for a particular email message. This is useful if you manage multiple brands or assets from a single sending domain. As the BIMI Group explains, this header signals a preference for a different selector. You might use this in a few scenarios:
- Multiple brands. If your company owns several distinct brands but sends email from one domain, you can use selectors to show the correct logo for each brand.
- Seasonal campaigns. You could create a holiday-themed version of your logo and use a selector to display it only during a specific campaign.
- A/B testing. You might want to test different logo variations to see how they impact recipient engagement.
To use it, you'd add a header like BIMI-Selector: v=BIMI1; s=yourselector;, where 'yourselector' corresponds to a specific BIMI record you've published in your DNS (e.g., yourselector._bimi.yourdomain.com).
The final verdict
So, to directly answer the question: No, BIMI does not typically require the sender to add a new header. Its validation status is simply recorded in the existing Authentication-Results header by the receiving server.
The only exception is the optional BIMI-Selector header, which is an advanced feature for managing multiple logos. For most senders implementing BIMI, the focus should be entirely on achieving DMARC enforcement and publishing the correct DNS records, not on modifying email headers.
