Guides on DNS resilience, email security and platform updates.
Welcome to the CaptainDNS blog. We share feedback to secure your DNS zones, improve your performance and track the evolution of the email ecosystem.
CaptainDNS · December 26, 2025
NextDNS is a customizable DNS resolver: DoH/DoT encryption, filtering, profiles, and logs. Here’s how to deploy it cleanly at home or in an SMB.
CaptainDNS · December 24, 2025
AdGuard DNS is a public DNS resolver that can block ads/trackers (and, in Family mode, adult content). Addresses, DoH/DoT/DoQ, and an action plan.
CaptainDNS · December 23, 2025
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.
CaptainDNS · December 19, 2025
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.
CaptainDNS · December 17, 2025
Add the CaptainDNS MCP server to ChatGPT and use 3 widgets to troubleshoot DMARC/DNS and analyze email headers without leaving the conversation.
CaptainDNS · December 16, 2025
Putting your logo in the inbox: what you actually need to configure in DNS for BIMI, and how to choose between VMC and CMC.
CaptainDNS · December 15, 2025
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.
CaptainDNS · December 10, 2025
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.
CaptainDNS · December 8, 2025
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.
CaptainDNS · December 7, 2025
Detailed postmortem on wiring a ChatGPT Apps SDK UI component to visualize the CaptainDNS SPF/DKIM/DMARC/BIMI audit.
CaptainDNS · December 5, 2025
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.
CaptainDNS · December 4, 2025
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.
CaptainDNS · December 1, 2025
Panorama of encrypted DNS transports at the end of 2025: performance, network impact, security, and an action plan for infra teams.
CaptainDNS · November 27, 2025
How we wired CaptainDNS to AIs through MCP: architecture, HTTP+SSE transport, JSON-RPC, 424 errors, timeouts, and what we learned along the way.
CaptainDNS · November 21, 2025
Before plugging CaptainDNS into AIs, you need to understand what the Model Context Protocol (MCP) is and what it really enables. A short MCP ABC, then first steps for CaptainDNS.
CaptainDNS · November 13, 2025
Revision -11 formalizes Local-Part Selectors (lps=), clarifies the discovery path, reaffirms SVG/SVGZ logos and reiterates DMARC and header requirements.
CaptainDNS · November 13, 2025
Your logo changed but inboxes still display the old one? It is not only a DNS issue: mailbox providers cache BIMI assets. Discover how the cache layers work and how to plan a smooth BIMI migration.
CaptainDNS · November 7, 2025
Diagnose, archive, share, then monitor: CaptainDNS now supervises the full lifecycle of a DNS query from the first lookup to automated watch jobs.
CaptainDNS · November 6, 2025
Starting in November 2025, Google enforces new security requirements for bulk senders: full SPF/DKIM/DMARC authentication, TLS encryption and strict unsubscribe management.
CaptainDNS · November 3, 2025
Everything you need to know about DKIM2 at the end of 2025: principles, new headers, coexistence with DKIM/DMARC, the IETF draft timeline and a readiness plan.
CaptainDNS · October 30, 2025
Behind 4.3M .fr domains, geography reveals a two-speed country: from 21 to 235 domains per 1,000 inhabitants depending on the department.
CaptainDNS · October 29, 2025
DMARCbis replaces RFC 7489, drops the PSL in favor of a DNS Tree Walk, adds 'psd', 'np' and 't', removes 'pct', 'ri' and 'rf', and splits reporting into two documents. Here's what it means...
CaptainDNS · October 23, 2025
ARC (Authenticated Received Chain) lets every relay forward, sign, and seal the authentication results it observed so the final server can decide whether to trust the message.
CaptainDNS · October 22, 2025
AI-automated phishing emails average a click-through rate of roughly 54%. At scale, automation can make these campaigns up to ×50 more profitable. Both figures come from the Microsoft Digital Defense Report 2025 (MDDR 2025).
CaptainDNS · October 20, 2025
EDNS Client Subnet (ECS) lets a DNS resolver pass a client address prefix to improve geolocation of the answers.
CaptainDNS · October 17, 2025
Ensure visibility of your domains by combining zone differences, active queries and propagation tests.
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.
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.
Certificates
Inspect CSRs, BIMI logos and VMC certificates before you deploy.
IP
Look up addresses, owners, reverse records and ranges.