Brand Indicators for Message Identification, or BIMI, is an email standard that allows you to display your brand's logo directly in your recipients' inboxes. The core idea, as Mailchimp notes, is to help customers avoid fraudulent emails by providing a verifiable visual cue. For BIMI to work, your domain must be authenticated with DMARC, ensuring that the emails are legitimately from you.
A basic BIMI setup involves publishing a single DNS record that points to your one official logo. However, the standard includes an often overlooked feature that provides much greater flexibility: the selector tag.
The s= tag in a BIMI record stands for 'selector'. A selector is an identifier that allows a domain owner to specify different logos for different email streams. Instead of having one logo for all emails sent from your domain, you can have many. You might have one for marketing, one for transactional emails, and another for a specific sub-brand.
When you use a selector, you aren't placing it in your default BIMI record. Instead, the selector becomes part of the DNS record's location itself. A standard default BIMI record is published at default._bimi.yourdomain.com. A record using a selector named 'marketing' would be published at marketing._bimi.yourdomain.com.
For a receiving mail server to know which logo to look up, the sender must include a special header in the email. This is called the BIMI-Selector header. The value of this header tells the server which selector to use.
The s= selector tag unlocks several powerful strategies for brand management in email. It gives you much more granular control over your brand's visual identity.
In short, the BIMI selector tag transforms BIMI from a simple, static feature into a dynamic branding tool. While not required for a basic implementation, it provides a level of control that is essential for any complex organization or savvy marketer looking to get the most out of their email presence.