Brand Indicators for Message Identification, or BIMI, is a powerful email standard that allows you to display your company's logo directly in your recipients' inboxes. It's a fantastic way to increase brand recognition and trust. As Kickbox notes, it's a standardized way to show authorized brand logos with your messages. Before you can get your logo to show up, however, you need to publish a specific DNS record with the correct prefix.
At its core, the BIMI record is a text (TXT) file that you add to your domain's DNS settings. This record tells email providers where to find your official logo and confirms that you've authenticated your emails properly.
The standard subdomain prefix for a BIMI DNS record is default._bimi. This means your full BIMI record will be located at a hostname like default._bimi.yourdomain.com. The word default is what's known as a "selector." While the BIMI specification allows for multiple selectors, default is the one universally used and looked for by mailbox providers. Fastmail's guide provides a clear example of this structure.
How the BIMI prefix works in practice
When an email provider like Gmail or Apple Mail receives a message from your domain, it performs a series of checks. If your email passes DMARC authentication, the provider then does a DNS lookup to see if you have a BIMI record published.
- The provider specifically looks for a TXT record at default._bimi.yourdomain.com.
- If found, the provider reads the record's content, which contains the URL to your brand's logo file (in SVG format) and, optionally, a URL for a Verified Mark Certificate (VMC).
- If everything is valid, your logo is displayed next to your email in the recipient's inbox, just as Mailgun describes.
Using BIMI with different subdomains
The BIMI standard is flexible when it comes to domain hierarchy. By default, a BIMI record published on your main organizational domain will also apply to all your subdomains.
However, you can also publish a different BIMI record on a specific subdomain. For example, if you send marketing emails from marketing.yourdomain.com, you could create a BIMI record at default._bimi.marketing.yourdomain.com. This specific record will override the main domain's BIMI record for any emails sent from that subdomain.
One crucial point to remember: for BIMI to work on any subdomain, the root domain must have a strict DMARC policy in place. As noted by Resend, your organizational domain must have a DMARC policy of p=quarantine or p=reject. A policy of p=none is not sufficient for BIMI.
In short, the default._bimi prefix is your starting point for implementing BIMI. By correctly configuring this DNS record on your main domain and any necessary subdomains, you unlock a simple yet effective way to improve your brand's visibility and trustworthiness in the inbox.
