
Cloudflare DNS (1.1.1.1): privacy, DoH/DoT, deployment
1.1.1.1 is Cloudflare's public DNS resolver. Here's how to use it properly (addresses, DoH/DoT/ODoH, tests, pitfalls) and deploy it.

1.1.1.1 is Cloudflare's public DNS resolver. Here's how to use it properly (addresses, DoH/DoT/ODoH, tests, pitfalls) and deploy it.

Quad9 (9.9.9.9) is a public DNS resolver focused on security and privacy: malware blocking, DNSSEC validation, and encrypted DoT/DoH options. Here's how to deploy it properly.

Add the CaptainDNS MCP server to ChatGPT and use 3 widgets to troubleshoot DMARC/DNS and analyze email headers without leaving the conversation.

Putting your logo in the inbox: what you actually need to configure in DNS for BIMI, and how to choose between VMC and CMC.

Gmail and Yahoo require a one-click unsubscribe via RFC 8058-compliant List-Unsubscribe headers. Here's the expected format, the server-side POST, and the compliance checklist.

IPv4 vs IPv6: address sizes, performance, security, NAT, DNS... Learn how to differentiate ipv4 and ipv6, what ipv6 vs ipv4 really means, the ipv4 and ipv6 difference for DNS, and how to keep both stacks coexisting.

Learn what Google Public DNS 8.8.8.8 is, how it works, its speed and reliability benefits, privacy drawbacks, how to configure it on Windows 11 or a router, and which alternatives (Cloudflare 1.1.1.1, OpenDNS, etc.) to consider.

Starting January 2026, Gmail will no longer continuously fetch messages from external mailboxes via POP ("Check mail from other accounts"). Impacts, timeline, and alternatives for Gmail and Google Workspace users and admins.

How we connected Auth0 to our CaptainDNS MCP server: dedicated audiences, PRM, Resource Parameter Compatibility Profile, JWT validation, identity propagation into profiles and api_requests, with optional auth today and protected tools ready for later.
DNS Lookup
Choose a DNS record type to search for.
Propagation & diagnostics
Compare resolvers worldwide and inspect returned answers.
Keep history, monitor your zones and automate recurring checks.
Email authentication
Tools to verify and validate your email authentication setup.
Deliverability
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.
Email tester
Send a test email and get instant authentication and deliverability feedback.
IP Blacklist Checker
Check if your IP is on email blacklists
Domain Blacklist Checker
Check if your domain is on URI blacklists
SPF Flattener
Flatten SPF records to reduce DNS lookups below the 10-lookup limit.
DKIM Selector Finder
Auto-discover all DKIM selectors for a domain via DNS brute-force.
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.
Web & Certificates
BIMI logos, VMC/CSR certificates and web page diagnostics.
BIMI logo lookup
Inspect a BIMI logo URL - format, metadata and live rendering - before rollout.
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.
Page size checker
Check if your page exceeds Google's 2 MB crawl limit.
IP
Look up addresses, owners, reverse records and ranges.