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How DNS, email, SSL, and web infrastructure actually work — explained clearly.
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Your Lighthouse Score Is 95 and Your Users Still Complain the Site Is Slow — Lab Data, Field Data, and Why They Diverge
How Gmail Decides Where Your Email Lands: Inbox, Promotions, and Spam Explained
Gmail routes email based primarily on engagement signals — opens, clicks, spam complaints, and whether recipients move messages to Primary. Here's how the three-tier system works, what signals determine Promotions vs. Primary, why list segmentation improves deliverability, and how Outlook differs from Gmail.
SSL Certificate Types: DV vs OV vs EV, Certificate Chains, and Preventing Expiry Outages
DV, OV, and EV certificates verify different things. Let's Encrypt is as secure as paid certs for encryption. The chain matters as much as the certificate itself. Here's what SSL certificates actually prove and how to prevent expiry outages.
Common Server Ports: Which Should Be Open and Which Must Be Firewalled
Every open port is a potential attack surface. Here's a practical reference of common ports — what they do, which should be publicly accessible, and which are commonly left dangerously exposed — with guidance on interpreting scan results.
Why Your Speed Test Looks Fine but Everything Still Feels Slow
High speed test numbers don't guarantee fast internet. Latency, bufferbloat, WiFi overhead, and ISP congestion all affect real-world performance in ways throughput tests don't capture. Here's how to read speed test results and diagnose actual slowness.
Subnetting Explained: CIDR Notation, Host Counts, and Practical Network Design
CIDR notation and subnetting make more sense once you see the pattern: each /1 increase halves the subnet. Here's how prefix lengths translate to host counts, common use cases from cloud VPCs to point-to-point links, and IPv6 subnetting philosophy.
Domain Due Diligence: Using WHOIS for SEO Research, Vendor Vetting, and Expiry Monitoring
WHOIS records reveal domain age, ownership history, expiry dates, and registration patterns that matter for SEO domain research, vendor due diligence, and operational monitoring — not just availability checking.
SPF PermError: Why the 10-Lookup Limit Breaks Email Authentication and How to Fix It
Adding third-party email services pushes SPF past the 10-lookup limit, causing PermError and DMARC failures. Here's how to count SPF lookups, why the limit is hit so easily, and the three solutions: IP replacement, flattening, and consolidation.
How to Read a Traceroute: What the Output Actually Tells You
A single high-latency traceroute hop usually isn't a problem. Asterisks don't mean the hop is down. Here's how to read traceroute output, identify where latency is actually introduced, and distinguish ICMP rate limiting from real network issues.
Reverse DNS and Email Deliverability: Why Your PTR Record Silently Matters
A missing PTR record silently degrades email deliverability. Here's how forward-confirmed reverse DNS works, why it matters for email authentication, who controls PTR records, and how reverse DNS is used in security investigation.
BIMI Setup Guide: How Email Logo Authentication Fits Into the Full Stack
BIMI is the capstone of email authentication — but it requires SPF, DKIM, and DMARC at p=reject to function. Here's the full setup guide, what Verified Mark Certificates are, which inboxes support it, and the most common misconfigurations.
DMARC Deployment: How to Move from p=none to p=reject Without Breaking Email
Most DMARC records are at p=none — monitoring mode with no actual protection. Here's the safe four-phase path from p=none to p=reject, how to read aggregate reports, the February 2024 Google/Yahoo requirements, and common mistakes.
MX Records and Email Delivery Failures: How to Diagnose and Fix Them
When email stops working, MX records are almost always part of the diagnosis. Here's how MX records control email delivery, how to debug bounces and delivery failures, common provider configurations, and the null MX for non-email domains.
