Authentication
Updated
BIMI (Brand Indicators for Message Identification)
Definition
BIMI (Brand Indicators for Message Identification) is a DNS TXT record that points mailbox providers to your brand logo so they can display it next to authenticated messages. It only works on domains with an enforced DMARC policy.
How it works
You publish a TXT record at default._bimi.yourdomain.com with v=BIMI1, an l= tag pointing to an HTTPS-hosted logo, and usually an a= tag pointing to a mark certificate.
When a message passes DMARC, a supporting provider fetches the record, validates the logo and certificate, and shows the logo as the sender avatar.
The logo must be an SVG in the SVG Tiny Portable/Secure (SVG Tiny PS) profile, square, with a solid background. Regular SVG exports from design tools usually need conversion.
Example
l= is the SVG Tiny PS logo, a= the mark certificate (VMC or CMC).
Why it matters
A logo in the inbox makes legitimate mail easier to recognize and harder to impersonate, because only domains with enforced DMARC qualify.
BIMI does not improve deliverability directly. Its real value is that getting it forces the authentication work (aligned SPF and DKIM, DMARC at quarantine or reject) that does.
Requirements
- DMARC at p=quarantine or p=reject on the organizational domain. p=none does not qualify.
- A logo in SVG Tiny PS format, served over HTTPS from a public URL.
- For Gmail and Apple Mail, a mark certificate: a Verified Mark Certificate (VMC), which requires a registered trademark, or at Gmail a Common Mark Certificate (CMC).
- BIMI is optional. Skip it until your DMARC is enforced and your authentication is clean.
How Lumail handles BIMI
BIMI is never required to send with Lumail. If a BIMI record is present but malformed (not v=BIMI1, or no HTTPS logo URL), Lumail shows an informational notice so you can fix or remove it.
Lumail checks the DMARC policy BIMI depends on, so you know when your domain is eligible.
Check a real message with the free mail tester or the spam tester.
Frequently asked questions
Does BIMI improve deliverability?
Not directly. Mailbox providers show the logo after authentication succeeds. The DMARC enforcement BIMI requires is what helps deliverability.
Do I need a VMC for BIMI?
Gmail and Apple Mail display logos only with a mark certificate. A VMC requires a registered trademark. Gmail also accepts a Common Mark Certificate, which does not. Some other providers show self-asserted logos without one.
Why is my BIMI logo not showing?
The usual causes are DMARC at p=none, a logo that is not SVG Tiny PS, a missing or invalid certificate, or low message volume. Providers also apply their own reputation thresholds before showing logos.
Related terms, tools and docs
- AuthenticationDMARCDMARC is a DNS TXT record at _dmarc.yourdomain.com that tells receivers what to do with mail that claims to be from your domain but fails authentication.
- AuthenticationDKIMDKIM (DomainKeys Identified Mail) is a cryptographic signature added to each email's headers.
- AuthenticationSPFSPF (Sender Policy Framework) is a DNS TXT record that lists which servers may send email using a domain in the envelope sender (Return-Path).
- DeliverabilitySender reputationSender reputation is the trust score mailbox providers assign to your sending domain and IP addresses, based on how recipients and their systems react to your mail.
- Free toolDMARC checkerRead a domain's DMARC policy, alignment and reporting tags.
- Free toolFree mail testerSend a real email and get an SPF, DKIM, DMARC and content report.
- Free toolDKIM checkerFetch a DKIM public key by selector and validate it.
- DocsHow to fix BIMIFix or remove a malformed BIMI record.
- DocsHow to strengthen DMARCMove from p=none to quarantine or reject.
- DocsSender healthHow Lumail measures sending health and authentication.
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