Before we dive into the specifics of the m= tag, it's important to understand what BIMI is. BIMI, which stands for Brand Indicators for Message Identification, is an email standard that allows you to display your company's logo next to your messages in the recipient's inbox. This provides a powerful visual cue, reinforcing your brand's identity and helping your emails stand out.
BIMI works through a special DNS record that you publish for your domain. This record contains several tags, such as v=BIMI1 to specify the version, l= to point to your logo's location, and sometimes, the m= tag. Understanding each component is key to a successful implementation.
The 'm=' tag explained
The m= tag stands for "Mark". Its purpose in the BIMI specification is to provide a reference to evidence of the sender's trademark rights for the logo being displayed. The value of this tag would be an identifier issued by a Mark Verifying Authority (MVA).
An MVA is a third-party organization responsible for verifying that a brand has the legal right to use a specific logo, typically through a registered trademark. The idea was that the m= tag would contain a string or number that directly links to this verification record. However, in practice, this system is not how BIMI logo verification has been implemented.
The role of VMCs and the 'a=' tag
The current, and required, method for verifying logo ownership for BIMI is through a Verified Mark Certificate (VMC). A VMC is a digital certificate, much like an SSL certificate for a website, that proves your organization has the right to use your logo. Certificate Authorities (CAs) like DigiCert or Entrust are responsible for vetting your trademark and issuing the VMC.
This VMC is referenced in the BIMI DNS record using the a= tag (which stands for "authority"), not the m= tag. The a= tag contains a URL pointing to your VMC file. Because the VMC itself serves as the proof of trademark, the m= tag became redundant.
Should you use the 'm=' tag?
No, you should not include the m= tag in your BIMI record at this time. It is an optional tag that is not currently used or required by mailbox providers like Gmail or Yahoo.
- Focus on the VMC: Your priority should be obtaining a VMC from a registered Certificate Authority.
- Use the 'a=' tag: Your published BIMI record must include the v=BIMI1 tag, the l= tag (pointing to your SVG logo), and the a= tag (pointing to your VMC).
- Omit the 'm=' tag: Since it serves no function in the current BIMI ecosystem, including it is unnecessary and could potentially cause validation issues.
In summary, the m= tag is a relic of the early BIMI specification. While it was designed with a clear purpose, the industry has since adopted the VMC standard (via the a= tag) as the sole method for logo verification. For anyone implementing BIMI today, the focus should be squarely on getting a VMC and correctly configuring the other required tags.
