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Practical guides on email authentication, DNS security, and deliverability. Learn how to protect your domain and reach the inbox.
Learn about Google and Yahoo's sender requirements, DMARC enforcement momentum, the three pillars of email authentication, and a complete action checklist for domain owners.
7 min readUnderstand how SSL certificate chains work, the roles of root CAs, intermediate certificates, and leaf certificates, and how to diagnose common chain issues.
8 min readLearn what DNS propagation is, how DNS caching and TTL work, why changes aren't instant, and how to check propagation status across global resolvers.
8 min readLearn what the SPF 10 DNS lookup limit is, why it exists, what causes permerror, and how to fix it with SPF flattening, subdomains, and macros.
8 min readLearn what DANE is, how TLSA records work, how DANE compares to traditional CAs, and how it secures SMTP email and HTTPS connections with DNSSEC.
8 min readLearn how subnetting works with CIDR notation, subnet masks, and binary calculation. Calculate network addresses, broadcast addresses, and host ranges for any prefix length.
8 min readLearn why small businesses are top targets for email attacks and how to protect your organization with SPF, DKIM, DMARC, MFA, and employee training.
7 min readLearn what BIMI is, how it works with DNS records, SVG logos, and VMC certificates, which email clients support it, and how to set it up to display your brand logo in the inbox.
7 min readLearn how TLS, MTA-STS, DANE, and TLSRPT protect email in transit. Understand STARTTLS downgrade attacks, how to enforce encryption, and how to check your setup.
8 min readA comprehensive 15-item security checklist covering SSL, HTTPS, security headers, DMARC, DNS security, open ports, backups, and more — with free tools for every check.
9 min readLearn how IP geolocation works under the hood, how accurate it really is at different levels, and explore real-world use cases from fraud detection to CDN routing.
7 min readFind out whether domain age actually impacts SEO rankings. We break down Google's stance, correlation vs causation, and what truly matters for search visibility.
7 min readStep-by-step guide to checking DNS records. Learn about A, AAAA, MX, TXT, CNAME, NS records and how to diagnose common DNS issues.
7 min readComprehensive best practices for email authentication. Learn how to configure SPF, DKIM, and DMARC correctly to meet Google and Yahoo requirements.
8 min readEverything you need to know about WHOIS — how it works, what data it contains, GDPR impact, and how to perform lookups.
6 min readComplete guide to email server ports. Learn about SMTP, IMAP, POP3 ports, security implications, and how to check if ports are open.
7 min readLearn what DMARC is, how it protects your domain from email spoofing, and how to set it up step by step — including every DMARC tag explained.
6 min readUnderstand how SPF, DKIM, and DMARC work together to authenticate your emails and prevent spoofing. A clear comparison with setup order.
7 min readEverything you need to know about getting your emails delivered — from authentication and sender reputation to content optimization and monitoring.
8 min readLearn what email blacklists (DNSBLs) are, how they work technically, and get step-by-step delisting instructions for Spamhaus, Barracuda, and SpamCop.
7 min readStep-by-step guide to setting up DKIM for Google Workspace, Microsoft 365, and custom mail servers. Understand the record structure and avoid common mistakes.
8 min readA complete guide to every common DNS record type — what each record does, when to use it, real examples, and common DNS mistakes to avoid.
8 min readLearn how SSL/TLS certificates work, the differences between DV, OV, and EV validation, how HTTPS protects data in transit, and how to check any certificate.
7 min readUnderstand how attackers forge sender addresses for phishing and BEC, and learn how to stop them with SPF, DKIM, DMARC, and BIMI.
7 min readLearn why SMTP sends email in plaintext by default, how MTA-STS enforces TLS encryption, and how to set it up with DNS records and HTTPS policy files.
6 min read