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Guides
Practical, no-fluff guides on DNS, email deliverability, SSL and network troubleshooting — each one links to the tools that put it into practice.
What Is WHOIS Privacy and Should You Enable It?
Learn what WHOIS exposes about your domain, how WHOIS privacy and GDPR redaction hide it, the real pros and cons, and when you should actually enable it.
How to Verify Domain Ownership with a TXT Record
Step-by-step guide to verifying domain ownership with a DNS TXT record: get the token, add it at the right host, wait for propagation, plus examples and fixes.
Subnet Masks and CIDR Notation Explained
A clear guide to subnet masks and CIDR notation: network vs host bits, /24 vs 255.255.255.0, host counts, private ranges, subnetting, and IPv6 prefixes.
SSL Certificate Chains Explained: Root, Intermediate, and Leaf
Understand the SSL/TLS chain of trust — root CA, intermediate, and leaf certificates — why incomplete chains break mobile and API clients, and how to fix them.
The DNS SOA Record Explained
Understand the DNS SOA record: every field decoded (MNAME, RNAME, serial, refresh, retry, expire, minimum), how secondaries use it, and how to check yours.
Reverse DNS (PTR) and Why It Matters for Email Deliverability
Learn what reverse DNS and PTR records are, how FCrDNS works, why mail servers demand matching forward and reverse DNS, and how to set up and check your PTR.
How to Set Up MX Records for Custom Domain Email
Step-by-step guide to setting up MX records for a custom domain: pick a provider, add the right records and priorities, configure SPF, DKIM and DMARC, then verify.
MTA-STS and TLS-RPT: Enforcing Encrypted Email Delivery
Learn how MTA-STS and TLS-RPT enforce encrypted SMTP and stop downgrade attacks. A step-by-step guide to publishing the DNS records and HTTPS policy file.
IPv4 vs IPv6: The Differences and Why They Matter
IPv4 vs IPv6 explained: address formats, why IPv6 exists, notation and compression, NAT and end-to-end, dual-stack, and how to tell if you have IPv6.
HTTP Status Codes Explained (301, 302, 404, 410, 500 and More)
What HTTP status codes mean, when each one applies, and how they affect SEO. Covers 200, 301 vs 302, 304, 404 vs 410, 401 vs 403, 429 and 5xx errors.
HTTP Security Headers Explained: CSP, HSTS and More
A practical guide to HTTP security headers: what CSP, HSTS, X-Content-Type-Options, frame-ancestors, Referrer-Policy and Permissions-Policy do, with examples.
How to Fix SPF ‘Too Many DNS Lookups’ (PermError)
SPF allows only 10 DNS lookups before a PermError breaks authentication. Learn what counts, how to count yours, and how to fix and flatten a bloated record.
How to Fix DNS_PROBE_FINISHED_NXDOMAIN
What the DNS_PROBE_FINISHED_NXDOMAIN error means, why it happens, and step-by-step fixes for both visitors and site owners, from cache to DNS records.
How to Find the IP Address and Host Behind Any Website
A step-by-step guide to finding a website's IP address, hosting provider, and DNS host using DNS, WHOIS, ASN, and reverse DNS lookups, plus the CDN caveat.
DNS TTL Explained: What It Is and How to Choose It
Understand DNS TTL: how record caching works, common values like 300, 3600, and 86400, the trade-offs, lowering TTL before a migration, and how to check it.
How to Read DMARC Aggregate (RUA) Reports
Learn to read DMARC aggregate (RUA) reports: the XML structure, SPF and DKIM alignment, spotting spoofing, and moving safely from p=none to reject.
Choosing a Public DNS Resolver: 1.1.1.1 vs 8.8.8.8 vs Quad9
Compare Cloudflare 1.1.1.1, Google 8.8.8.8, Quad9, OpenDNS and AdGuard on privacy, security filtering, speed and encryption, then learn how to switch and test.
What Is BIMI and How to Show Your Logo in Email
Learn what BIMI is, why DMARC enforcement is required first, the SVG and VMC requirements, the DNS record format, and how to verify your BIMI setup.
What Is a CNAME Record? (And When to Use One)
A clear guide to CNAME records: how they differ from A records, the apex-domain limitation, CNAME flattening, common uses, pitfalls, and how to check one.
CAA Records Explained: Control Which CAs Can Issue Your Certificates
Learn how CAA DNS records let you whitelist which certificate authorities may issue TLS certificates for your domain, with syntax, examples, and how to check yours.
DNSSEC Explained: What It Is and Whether You Should Enable It
A plain-English explanation of DNSSEC: the problem it solves, how the chain of trust works, the trade-offs, and how to check if a domain is signed.
Email Deliverability Checklist: Why Your Email Goes to Spam (and How to Fix It)
A practical checklist for landing in the inbox instead of spam: authentication, reputation, list hygiene, content, and the checks to run on your own domain.
Open Ports Explained (and How to Check Them Safely)
What a network port is, what 'open' really means, the ports you should know, and how to safely check whether a port is reachable.
How to Fix 'Your Connection Is Not Private' and Other SSL Errors
What the 'Your connection is not private' warning really means, the common SSL/TLS error codes, and how to diagnose and fix each one.
What Is an ASN? (And How to Find Out Who Owns an IP Address)
Learn what an Autonomous System Number is, how IP addresses map to the organizations that run them, and how to find the owner of any IP.
How to Read a Traceroute (and Find Where the Slowness Is)
Understand every column of a traceroute, what high latency and timeouts really mean, and how to tell whether a problem is on your side or the network's.
DNS Record Types Explained: A, AAAA, MX, TXT, NS, CNAME and More
A plain-English guide to every common DNS record type, what each one does, when you would use it, and how to check it.
What Is My IP Address? (And How to Hide It)
What your IP address reveals, the difference between public, private, IPv4 and IPv6 addresses, and the real ways to hide or change it.
How to Check an SSL/TLS Certificate and Prevent Expiry Outages
Learn how to read an SSL/TLS certificate, check its expiry and chain, automate renewal with ACME, and set up monitoring so HTTPS never goes down.
How to Check DNS Propagation After Changing Records
Learn what DNS propagation really means, how TTL and caching cause delays, and how to check propagation across global resolvers after changing your records.
Why Your IP Is Blacklisted and How to Get Delisted
Find out why your IP landed on a DNS blocklist, how to check which lists flag it, and the step-by-step process to fix the cause and get delisted fast.
How to Set Up SPF, DKIM and DMARC for Email Authentication
Learn how to set up SPF, DKIM and DMARC records to stop email spoofing and boost deliverability. A step-by-step guide to authenticating your domain.