Log in
CaptainDNS

Propagation & diagnostics

Compare resolvers worldwide and inspect returned answers.

Email authentication

Tools to verify and validate your email authentication setup.

SPF syntax validator

Review include chains and DNS query limits before publishing changes.

SPF record inspector

Resolve the published TXT record, flag lookup limits and decode each mechanism.

DKIM syntax validator

Quickly check the syntax of your DKIM records.

DKIM record check

Resolve a selector and analyse the published DKIM TXT record.

DMARC syntax validator

Check rua/ruf destinations, alignment modes and the active policy before publishing.

DMARC record inspector

Resolve the published policy, surface diagnostics and confirm enforcement before switching to reject.

BIMI syntax validator

Validate BIMI tags, the logo fetch and the VMC certificate before publishing.

BIMI record inspector

Resolve the published BIMI record, inspect logo and VMC diagnostics in one place.

Email deliverability audit

Audit MX, SPF, DKIM and DMARC to confirm a domain is ready to send.

Mail header analyzer

Decode participants, authentication results and routing from raw headers.

DMARC record generator

Create compliant DMARC records with all policy and reporting options.

Text

Transform, encode and measure your content in seconds.

Text case converter

Convert any block of text to upper or lower case instantly.

Base64 encoder / decoder

Encode or decode any content in Base64 without leaving the browser.

Slug generator

Transform any sentence into an SEO-friendly slug in seconds.

Word & character counter

Measure the length of any text, with instant word and character counts.

Images

Preview and validate your BIMI logos before publishing.

BIMI logo lookup

Inspect a BIMI logo URL—format, metadata and live rendering—before rollout.

Certificates

Inspect CSRs, BIMI logos and VMC certificates before you deploy.

CSR parser

Inspect a CSR, extract subject details, fingerprints and requested SANs.

VMC inspector

Inspect a Verified Mark Certificate—issuer, validity and SAN coverage—before you publish BIMI.

IP

Look up addresses, owners, reverse records and ranges.

Reverse lookup

Resolve a PTR record and validate DNS consistency.

IP WhoIs

Identify the owner of an IP range and its contacts.

IPv4 netmask

Calculate network, broadcast and usable hosts for any IPv4 block.

My IP address

Detect your IPv4/IPv6 addresses and their geolocation.

BIMI syntax checker

What a BIMI record contains

Brand Indicators for Message Identification (BIMI) points mailbox providers to an SVG logo and, when required, to a Verified Mark Certificate (VMC). The TXT record lives at default._bimi.<domain> and is made of semicolon-separated key/value pairs.

Example BIMI record

v=BIMI1; l=https://brand.example/logo.svg; a=https://brand.example/vmc.pem

Mandatory and optional tags

  • v — the version. BIMI1 is currently the only accepted value.
  • l — HTTPS URL of the Tiny-PS compliant SVG logo to display.
  • a — HTTPS URL of the VMC. Optional, but required by providers that demand a verified mark.
  • Additional non-standard tags must be avoided; the validator flags unknown keys so you can keep the record interoperable.

What this validator checks

  • Basic syntax and presence of the required tags.
  • HTTPS scheme, redirects and content type of the logo URL.
  • Tiny-PS constraints such as viewBox, forbidden attributes and foreign elements.
  • Download status and metadata of the VMC certificate when provided.

Before you publish

  • Enforce DMARC with a policy of quarantine or reject; BIMI will be ignored otherwise.
  • Host the SVG logo on HTTPS, without authentication and under your control.
  • Keep the SVG minimal: square viewBox, no external references, no scripts and explicit Tiny-PS compliance.
  • Ensure the VMC is up to date and issued for the domains you intend to display.

The validator highlights every warning, error and piece of metadata so you can ship a BIMI record that providers accept without guessing.

BIMI syntax checker - CaptainDNS