A missing brand logo can originate in DNS discovery, message eligibility, asset retrieval, certificate evidence, image validation or the recipient interface. Diagnose those stages separately. An HTTPS timeout is not proof that the sending domain failed DMARC, and a successful mail delivery does not show that a receiver retrieved the logo.
Identify the failed asset
References: Source §4.3, Source §7.3, Source §7.6.
Record the evaluated From domain, BIMI selector, discovery time and complete assertion record. Resolve l= and a= into separate asset requests. The first identifies an indicator location; the second identifies authority evidence when supplied. Do not confuse the HTTPS server certificate protecting a download with the mark certificate contained in the downloaded evidence. They serve different purposes and can fail independently.
The core BIMI draft revision 15 describes HTTPS locations in section 4.3 and retrieval and validation in sections 7.3–7.6. It remains work in progress, not an issued RFC. Google additionally documents its own HTTPS hosting requirements. These sources support the retrieval checks, but neither supplies a universal timeout for every mailbox provider. BIMI draft 15.
Preserve the TLS security check
Test the exact hostname and path anonymously. Record DNS answers, connection timing, certificate identity, trust-chain outcome, HTTP status and returned bytes. A browser that already trusts a corporate inspection certificate may not reproduce an external receiver's trust store. Likewise, an authenticated administrative session can conceal a public-access problem.
Do not use a certificate-verification bypass as a production fix. Repair the hostname binding, missing intermediate chain, expired certificate or inaccessible path. MTA-STS and DANE concern SMTP transport policy; changing their records does not repair the HTTPS certificate serving a BIMI logo. A successful TLS handshake still leaves status, content and mark-evidence validation to check.
Reproduce positive and negative requests
The retained fixture, executed on 7 November 2026, created a temporary certificate for localhost, starts a loopback HTTPS server and explicitly trusts that certificate in the test client. It requested an SVG path, then repeated without the lab trust anchor, with a deliberately incorrect server hostname, and against a delayed response with a shorter client timeout. The retained observed outcomes distinguish a successful response, untrusted certificate, hostname mismatch and read timeout. Each observed case retains a UTC timestamp, loopback IP and port, requested hostname and path, client timeout, trust configuration, served-certificate fingerprint and the exact verification failure where available. The public lab certificate metadata records subject, issuer, validity and the single-certificate chain; the private key is discarded.
The timeout is a local testing choice, not a provider rule. The SVG is a harmless transport marker, not an approved brand asset. That exercise ran real TLS locally but does not validate a mark certificate, publish DNS or prove Gmail, Yahoo or any other receiver can fetch a production asset. The current review inspects those retained receipts and public certificate bytes offline; it does not rerun the network experiment. Retain the execution log rather than presenting expected results as observed production behavior.
Repair the responsible layer
For connection failures, inspect network reachability and the hosting service. For TLS failures, inspect the certificate actually served. For HTTP errors, investigate access controls, bot challenges, routing and content deployment. Compare IPv4 and IPv6 paths when both are advertised. Keep requests bounded to avoid generating a large incident workload against an already degraded endpoint.
After repair, repeat the same request with verification enabled and compare the asset digest with the approved release. Then perform authorized mailbox tests across the intended provider and client combinations. Asset retrieval, BIMI validation and visible display need separate evidence. Do not close a logo incident solely because a web dashboard reports the host as healthy.