What Is BIMI and How Does It Strengthen Inbox Security?
BIMI (Brand Indicators for Message Identification) is an email authentication standard that strengthens inbox security while enhancing brand visibility. By displaying verified brand logos in supported inboxes, BIMI helps users quickly identify legitimate emails and avoid phishing attempts. Built on foundational protocols like SPF, DKIM, and DMARC, BIMI requires strict authentication enforcement and logo validation through Verified Mark Certificates (VMCs) or Common Mark Certificates (CMCs). The result is improved trust, reduced impersonation risk, and stronger engagement for organizations that rely on email as a core communication and marketing channel.
Email represents far more than a simple communication tool. It's also a powerful branding strategy, capable of building both trust and awareness for your organization. Unfortunately, it's also a significant source of risk: threat actors view the modern inbox as the ultimate gateway, relying on emails for phishing attacks and business email compromise.
These hazards make users more reluctant than ever to open their emails. This can be problematic from a branding perspective; those carefully designed marketing emails accomplish little if they're never opened in the first place.
This is where BIMI comes into play. Simultaneously strengthening security and branding, BIMI delivers a visible trust signal supported by behind-the-scenes authentication. Inbox providers reward authenticated senders with display features, helping users more easily identify legitimate emails and engage with them.
What is BIMI?
The email specification commonly referred to as BIMI references Brand Indicators for Message Identification, a standard that allows organizations to display verified brand logos in supported inboxes such as Gmail, Yahoo Mail, and more. BIMI creates a structured method for linking authenticated emails with a brand’s validated visual identity, helping legitimate senders stand apart from impersonators and spoofers.
Collectively introduced by well-known email clients, BIMI builds on existing authentication standards to add a visible trust signal in the inbox. As a result, recipients recognize and trust verified senders, leading to all-around improvements in security and brand awareness.
How does BIMI improve trust?
BIMI fuels trust through the power of visual recognition. Following successful authentication, the BIMI protocol ensures that logos are prominently displayed within email inboxes. This provides an instant marker of credibility. Recipients gain higher confidence that logo-equipped emails originate from authenticated senders.
To ensure that these logos are legitimate, BIMI relies on mark certificates that validate the relationship between a brand, its logo, and the email sending domain. Different types of mark certificates are available depending on the level of protection needed and the trademark status of the logo.
With a Verified Mark Certificate (VMC), a trusted certificate authority confirms both the logo and the email sending domain, with validation tied to a registered trademark. This level of assurance is well suited for organizations that require strong brand authentication.
For organizations without a registered trademark, a Common Mark Certificate (CMC) offers an alternative path to BIMI. CMCs verify that a logo has been in consistent use for at least one year and, like VMCs, require enforced email authentication policies to ensure only authenticated senders can display their logos.
Role in brand visibility
BIMI's security implications should be top of mind, but this is also worth pursuing from a branding perspective. Simply put, logos stand out within crowded email inboxes, but these cannot be displayed without BIMI. Taking the steps to implement BIMI can cut through the noise of today's jam-packed inbox, attracting attention through visual differentiation and, over time, through the power of repeated exposures.
How does BIMI work?
BIMI relies on a complex series of authentication standards that can be identified based on their commonly used acronyms: DMARC, SPF, and DKIM, to name a few. These work in tandem to help ensure that fraudulent or spoofed emails do not reach recipients' inboxes, a necessary element for BIMI effectiveness.
- SPF (Sender Policy Framework): Domain owners use the SPF protocol to clarify which mail servers are permitted to send emails. Receiving servers then check SPF records to verify legitimacy. SPF forms the basis of domain-centered email authentication and is a cybersecurity must, only allowing authorized individuals or organizations to send on behalf of domains.
- DomainKeys Identified Mail (DKIM): As a digital signature, DKIM relies on public key cryptography for authenticating individual emails. One of the core goals of DKIM is to prevent content from being altered in transit so there's no question as to whether messaging originated from the domain in question.
- DMARC (Domain-based Message Authentication, Reporting, and Conformance): If emails fail authentication checks, DMARC determines what happens next. Building on SPF and DKIM, this establishes policies for failed checks. Through DMARC, domain owners gain greater control over the handling of unauthenticated messages. This can have a profound impact on email deliverability.
- DNS (Domain Name System) record: BIMI involves a specific type of DNS record. In general, DNS records are meant to link internet protocol (IP) addresses and domain names.
Authentication prerequisites
Several stringent standards must be met before BIMI can be enabled. These standards are essential security controls to meet today's cyber challenges and they ensure that BIMI fulfills core functions such as improving trust and preventing phishing. Once SPF and DKIM validation are established, you must then set your DMARC policies to quarantine or reject. A quarantine policy sends suspicious messages to the spam or junk folder, while a reject policy blocks them entirely, preventing delivery. Finally, domain alignment ensures that the domain highlighted in the 'from' address reflects the domain authenticated via SPF and DKIM.
Generating BIMI DNS record
Enabling BIMI involves publishing DNS TXT records that point to desired brand logos. These records should be published at default._bimi.[yourdomain.com], which provides a standardized location in which BIMI information can be found and verified. The TXT record should reference the BIMI version and should also include the HTTPS link to the brand logo file, which should be available in the SVG Tiny Portable/Secure (SVG P/S) format to ensure full compatibility.
BIMI logo verification with VMCs and CMCs
Logo verification is central to the BIMI process. As mentioned previously, there are two types of mark certificates available, typically selected based on whether a logo is trademarked. Brands with registered trademarks will ideally obtain Verified Mark Certificates, as these provide a higher level of assurance and are accepted in more mailbox providers.
Common Mark Certificates are also a strong solution, particularly for SMBs or organizations without trademarked logos, as they validate logo use and enable BIMI logo display in supported inboxes.
Inbox display process
A series of steps must occur before verified logos can be displayed in email inboxes. This begins as sending domains authenticate emails via DMARC. As providers receive emails, strict checks confirm that the appropriate BIMI records are in the DNS. This makes it possible for email clients to retrieve verified SVG-Tiny logos via HTTPS. These can be displayed in the inbox previews once authentication and verification criteria are met.
What are the requirements to implement BIMI?
Most organizations can take advantage of BIMI, but certain authentication and verification requirements must be met first. These include:
- DMARC enforcement: DMARC policies must be strategically set before BIMI can go into effect. Remember, p=quarantine ensures that suspicious emails are sent to the spam folder, while p=reject blocks problematic emails outright.
- SVG-Tiny logo: The Scalable Vector Graphics offers a streamlined version that promises to load quickly and render consistently. For BIMI purposes, this logo should be properly formatted and must remain free of unsupported elements.
- TXT record: Highlighting the location of the verified SVG-Tiny logo, the TXT record should be correctly published, with the BIMI selector ensuring that email providers can easily locate and securely display the logo in question.
- VMC or CMC: BIMI can be supported by VMC or CMC certificates. Both validate logo ownership, but VMCs call for trademarked logos, which are not required for CMCs.
Benefits of BIMI for organizations
BIMI offers far-reaching benefits, empowering organizations to strengthen both email security and branding through the power of verified logos. It represents just one of many email security practices worth implementing, but it can be one of the most impactful because it offers clear benefits beyond phishing defense. Advantages include:
Brand trust and reputation advantages
BIMI helps reduce phishing and impersonation risks by ensuring only authenticated senders can display verified brand logos in the inbox. By building on DMARC enforcement and other authentication standards, BIMI makes it easier for users to trust logo-displaying emails and avoid interacting with suspicious messages.
Marketing and engagement advantages
Amid the ongoing relevance of email marketing, BIMI helps brands overcome some of the most frustrating marketing roadblocks: low email open rates that stem from limited user trust. BIMI improves trust through visual recognition which can contribute to increased engagement and open rates.
Users who take that crucial first step and open emails get the opportunity to actually engage with content, and, as they continue to open emails with logos over time, they become more loyal to the brands featured in these emails.
Bring BIMI into your email protection strategy with Sectigo
Sectigo is a leading certificate authority offering Verified Mark Certificates and Common Mark Certificates that support BIMI and help brands display trusted, verified logos in supported inboxes. These certificates provide the validation needed to reinforce authenticity and help protect your brand from impersonation.
Whether you’re just getting started with email authentication or you’re ready to display your logo in inboxes worldwide, Sectigo can supply the certificate solutions you need. Learn more about how VMCs and CMCs help strengthen trust with every email.