BIMI, which stands for Brand Indicators for Message Identification, is a powerful email standard that allows you to display your company's logo directly in your recipients' inboxes. It works alongside DMARC, SPF, and DKIM to build trust and brand recognition. A standard BIMI record is a TXT record in your DNS that points to your logo file.
A simple BIMI record might look like this: v=BIMI1; l=https://yourbrand.com/logo.svg;. However, the BIMI specification includes several optional tags for more advanced configurations, and one of the most useful is the d= tag.
What is the purpose of the BIMI 'd=' tag?
The primary purpose of the BIMI d= tag, which stands for 'delegated', is to instruct mailbox providers to look at the BIMI record of a different domain. It's a method of delegation. Instead of hosting a BIMI record with a logo URL on every single one of your domains, you can use the d= tag to point them all to a single, authoritative domain where the primary BIMI record is managed.
This is especially useful for large organizations that manage multiple domains. Imagine a global company with country-specific domains like mybrand.co.uk and mybrand.de. Instead of duplicating the BIMI record on both, they can delegate to their main mybrand.com domain. If the company ever updates its logo, it only needs to change one DNS record on the main domain.
How the 'd=' tag works with BIMI selectors
The d= tag works within the broader BIMI framework, which also includes 'selectors'. As the BIMI Group explains, BIMI allows brands to control the logos displayed with their emails. Selectors offer a way to refine that control.
While selectors let you use different logos for different email streams within the *same* domain (for example, one for marketing and another for transactional emails), the d= tag is for delegating BIMI authority across *different* domains.
Here’s how it works in practice for a domain called secondary-brand.com that wants to use the BIMI configuration from main-brand.com.
- Main Domain: The DNS for main-brand.com has a standard BIMI record: default._bimi.main-brand.com TXT "v=BIMI1; l=https://main-brand.com/logo.svg;"
- Delegated Domain: The DNS for secondary-brand.com uses the d= tag to point to the main domain: default._bimi.secondary-brand.com TXT "v=BIMI1; d=main-brand.com;"
- Result: When an email provider receives a message from contact@secondary-brand.com, it sees the d=main-brand.com tag. It then performs a new lookup for the BIMI record at main-brand.com and uses that logo.
In summary, the d= tag is a simple but effective tool for centralizing your BIMI management. It reduces administrative overhead and ensures brand consistency across multiple domains, making it a valuable feature for any organization with a complex domain portfolio.
