--- title: "Blog | Email Security and Deliverability | DuoCircle" description: "Plain-English guides on SPF, DKIM, DMARC, BIMI, phishing protection, and email deliverability from the DuoCircle team." image: "https://www.duocircle.com/images/og-default.png" canonical: "https://www.duocircle.com/blog/" --- ## Browse by topic Announcements (381) Email Security (303) Phishing Protection (150) DMARC (127) Email Services (77) Email Hosting (50) Data Privacy (38) Outbound SMTP (26) [ News GitHub Code Leak, 7-Eleven Breached, NYC Patient Exposure – Cybersecurity News \[May 18, 2026\] Massive cyberattacks hit GitHub, 7-Eleven, NYC hospitals, and more. Explore the biggest cybersecurity threats and breaches from May 18, 2026. May 25, 2026 ](/blog/cybersecurity-news-update-week-21-of-2026/)[ Intermediate Preventing Business Email Disruption Through An Invalid DKIM Selector Fix Process Prevent business email disruption by fixing invalid DKIM selectors quickly to improve email authentication, deliverability, and domain trust. May 25, 2026 ](/blog/preventing-business-email-disruption-invalid-dkim-selector-fix-process-guide/)[ Intermediate 20 Common Threats To Domain Reputation Protection And How To Avoid Them Learn the top threats to domain reputation and how to avoid them to keep your email and online presence secure. May 22, 2026 ](/blog/20-common-threats-domain-reputation-protection-how-to-avoid-them/)[ Intermediate 20 Common Threats To Domain Reputation Protection And How To Avoid Them Learn the top threats to domain reputation and how to avoid them to keep your email and online presence secure. May 22, 2026 ](/blog/20-common-threats-to-domain-reputation-protection-and-how-to-avoid-them/)[ Foundational What Is GPS Spoofing? A Detailed Guide Learn what GPS spoofing is, how it manipulates location data, the risks it creates, and the methods used to detect and prevent spoofing attacks. May 21, 2026 ](/blog/what-is-gps-spoofing-a-detailed-guide/)[ Intermediate Using Machine Learning For Malicious Email Detection And Phishing Defense Machine learning helps detect malicious emails and phishing attacks faster, improving email security and reducing cyber threats. May 20, 2026 ](/blog/using-machine-learning-for-malicious-email-detection-and-phishing-defense/)[ Intermediate 7 Quick Fixes For SPF Authentication Failure In Microsoft 365 And Exchange Online Fix SPF authentication failures in Microsoft 365 and Exchange Online with 7 quick solutions to improve email delivery, stop spoofing, and protect domains. May 19, 2026 ](/blog/7-quick-fixes-spf-authentication-failure-microsoft-365-exchange-online/)[ News Cisco SD-WAN Flaw, Critical NGINX Exploit, Foxconn Ransomware Attack – Cybersecurity News \[May 11, 2026\] Critical cybersecurity threats emerge as Cisco SD-WAN, NGINX, Microsoft Exchange, and PAN-OS flaws face active exploitation worldwide. May 18, 2026 ](/blog/cybersecurity-news-update-week-20-of-2026/)[ Foundational 11 Common Malware Types and How to Spot Them Learn about 11 common malware types, how they spread, and the warning signs to help protect your devices and data online. May 15, 2026 ](/blog/11-common-malware-types-and-how-to-spot-them/)[ Email Services 8 min 5 Reasons To Test SPF Configuration Before Sending Emails Testing your SPF configuration before a campaign goes live is a core part of modern email authentication. May 14, 2026 ](/blog/5-reasons-to-test-spf-configuration-before-sending-emails/)[ Email Security 13 min Your Vendors Are Your Weakest Link: How Third-Party Email Compromise Doubled in One Year and What SMBs Can Do About It A data-driven analysis with 20+ primary-source statistics from Verizon, IBM, SecurityScorecard, the FBI, the World Economic Forum, and others. May 14, 2026 ](/blog/third-party-email-compromise-doubled-smb-vendor-security-risks-solutions/)[ Email Services 8 min How To Validate A DMARC Record Generator Output Before Publishing DNS Changes A DMARC record generator can simplify the process of creating a DMARC policy, but generating the record is only the first step. May 13, 2026 ](/blog/how-to-validate-a-dmarc-record-generator-output-before-publishing-dns-changes/)[ Announcements 8 min Zara Data Exposed, Medtronic Cyberattack Confirmed, Trellix Repository Breached – Cybersecurity News \[May 04, 2026\] Here’s your weekly roundup of the most important cybersecurity stories from the past week, covering major data breaches, critical vulnerabilities. May 11, 2026 ](/blog/cyber-security-news-update-week-19-of-2026/)[ Email Services 8 min 7 DKIM DNS Configuration Strategies For Hybrid Cloud Email Systems Contemporary businesses seldom depend on a singular email setup. May 8, 2026 ](/blog/7-dkim-dns-configuration-strategies-for-hybrid-cloud-email-systems/)[ Email Security 5 min Email Monitoring Tools: A Complete Guide to Protecting Your Email Ecosystem Email continues to be one of the most essential communication channels for businesses—but it’s also one of the most targeted by cyber threats. May 7, 2026 ](/blog/email-monitoring-tools-guide-protecting-your-email-ecosystem-security/)[ Cybersecurity 19 min The State of Cybersecurity in 2026: What the Data Tells Us, What It Means, and What to Do Next A data-driven analysis of 26 primary-source statistics from institutional reports by the World Economic Forum, IBM, Verizon, Cisco, Accenture, ISC2, NIST. May 6, 2026 ](/blog/state-cybersecurity-2026-data-insights-risks-trends-actions-next-steps/)[ Email Services 8 min SPF Lookup Failure Troubleshooting: Why Your SPF Record Breaks And How To Fix It Email authentication serves as the foundation for effective email deliverability. May 6, 2026 ](/blog/spf-lookup-failure-troubleshooting-why-your-spf-record-breaks-and-how-to-fix-it/)[ Email Security 8 min BIMI in 2026: What the Certificate Authority Does, and What Your DMARC Tool Does BIMI confuses buyers because two different vendors handle two different jobs. Here is the clean split between VMC procurement (a Certificate Authority function) and BIMI hosting (what your DMARC reporting tool actually does). May 5, 2026 ](/blog/bimi-2026-what-the-ca-does-what-your-dmarc-tool-does/)[ SPF Records 7 min When SPF Lookup Limits Actually Break Things: The 10-Lookup Rule, Permerror, and How to Stay Under It The SPF 10-DNS-lookup limit silently breaks email authentication once you exceed it. Here is how to diagnose a permerror, why even careful organizations end up over the limit, and the fix options that actually work. May 5, 2026 ](/blog/when-spf-lookup-limits-actually-break-things/)[ Outbound SMTP 7 min Office Copiers Can't Authenticate to Microsoft 365 Anymore: Why It Broke and How to Fix It Your scan-to-email died after a Microsoft 365 update. Here's why basic auth and SMTP AUTH got disabled, the three options your IT team actually has, and the fastest reliable fix. May 5, 2026 ](/blog/office-copiers-cant-authenticate-to-microsoft-365-the-fix/)[ Email Services 7 min 11 SPF Validation Tool Checks You Should Run Before Sending Bulk Emails Email marketing campaigns have the potential to enhance engagement, boost conversions. May 5, 2026 ](/blog/11-spf-validation-tool-checks-you-should-run-before-sending-bulk-emails/)[ DMARC 7 min DMARC at p=none Is a Setup State, Not a Deployment Publishing a DMARC record at p=none is the starting line, not the finish line. Here is what p=none actually does, what it does not, and how to move to enforcement without breaking legitimate mail. May 5, 2026 ](/blog/dmarc-p-none-is-a-setup-not-a-deployment/)[ Announcements 12 min Medtronic Cyberattack Confirmed, cPanel Ransomware Wave, Root Access Granted , Cybersecurity News \[April 27, 2026\] Here’s your weekly roundup of the most significant cybersecurity stories from the past week, covering major data breaches, critical vulnerabilities. May 4, 2026 ](/blog/cyber-security-news-update-week-18-of-2026/)[ Email Services 6 min How Poor Email Testing Is Silently Costing SaaS Companies Thousands Email is one of the most critical communication channels for SaaS companies. May 4, 2026 ](/blog/poor-email-testing-silently-costing-saas-companies-thousands/)[ Email Security 12 min Shadow AI in the Inbox: How Employees Using Unauthorized AI Tools Are Creating a New Email Security Crisis A data-driven analysis with 20+ statistics from Verizon, IBM, Cisco, KPMG, LayerX, Microsoft, the World Economic Forum, and others. May 4, 2026 ](/blog/shadow-ai-email-security-risks-from-unauthorized-employee-ai-tools/)[ SPF Records 8 min How SPF Record all Affects Email Routing Across Hybrid Cloud Environments In today’s digital landscape, especially within hybrid cloud frameworks, email authentication has become increasingly vital. Apr 30, 2026 ](/blog/how-spf-record-all-affects-email-routing-hybrid-cloud-environments/)[ DMARC 5 min Why DIY-ing DMARC could cost you more than you think Why DIY-ing DMARC could cost you more than you think. Apr 30, 2026 ](/blog/why-diy-ing-dmarc-could-cost-more-than-you-think/)[ Email Services 7 min 7 Critical Factors to Consider Before You Buy SMTP Relay Services Email remains an essential communication tool for businesses, utilized for everything from transactional notifications to marketing initiatives and customer. Apr 29, 2026 ](/blog/7-critical-factors-before-you-buy-smtp-relay-services/)[ Email Security 12 min DMARC, SPF, and DKIM in 2026: Why Email Authentication Is Now a Regulatory Requirement, Not Just a Best Practice A data-driven analysis with 20+ statistics from EasyDMARC, Google, Microsoft, IBM, Verizon, CISA, and the PCI Security Standards Council. Apr 29, 2026 ](/blog/dmarc-spf-dkim-2026-email-authentication-regulatory-requirement-best-practice/)[ Email Security 8 min Designing A Custom Dkim Architecture For High-Volume Email Senders Organizations that send large volumes of emails, including software-as-a-service (SaaS) platforms, marketing automation providers. Apr 28, 2026 ](/blog/designing-custom-dkim-architecture-for-high-volume-email-senders/)[ Phishing Protection 11 min AI-Generated Phishing Has Eliminated the Typo: Why Traditional Email Filters Are No Longer Enough A data-driven analysis for security leaders, IT teams, and MSPs, with 20+ primary-source statistics from Microsoft, IBM, FBI IC3, KnowBe4, Verizon, Cisco. Apr 28, 2026 ](/blog/ai-generated-phishing-eliminates-typos-making-traditional-email-filters-ineffective/)[ Announcements 5 min Sri Lanka Cyberattack, SilentGlass Threat Defense, Rituals Data Breach, Cybersecurity News \[April 20, 2026\] Sri Lanka Cyberattack, SilentGlass Threat Defense, Rituals Data Breach, Cybersecurity News \[April 20. Apr 27, 2026 ](/blog/cyber-security-news-update-week-17-of-2026/)[ Email Services 8 min How To Migrate From Windows SMTP Server To Cloud-Based SMTP Without Downtime Transitioning from a Windows-based SMTP server to a cloud-hosted solution has evolved beyond simple modernization; it’s now a key strategic initiative aimed at. Apr 24, 2026 ](/blog/how-migrate-windows-smtp-server-to-cloud-smtp-without-downtime/)[ Email Services 17 min Trust by Design: Rethinking DKIM Settings for Modern Email Email trust is no longer a background technical detail, it’s the foundation of how brands communicate, protect users. Apr 23, 2026 ](/blog/trust-by-design-rethinking-dkim-settings-for-modern-email/)[ Email Services 16 min 5 Best DKIM Record Examples To Understand Selectors, Key Lengths, And TXT Formatting Why these DKIM record examples matter A well-formed DKIM record is the foundation of email authentication. Apr 21, 2026 ](/blog/5-best-dkim-record-examples-selectors-key-lengths-txt-formatting/)[ Announcements 5 min UK Cyber Surge, Poland Incident Surge, Japan Shipping Attack, Cybersecurity News \[April 13, 2026\] UK Cyber Surge, Poland Incident Surge, Japan Shipping Attack, Cybersecurity News \[April 13. Apr 20, 2026 ](/blog/cyber-security-news-update-week-16-of-2026/)[ Email Security 5 min Enterprise email security: Here’s what you should know about it When your organization operates at scale, emails don’t go out from one domain; they are sent from marketing platforms, HR systems, finance tools. Apr 16, 2026 ](/blog/email-security/enterprise-email-security-heres-what-you-should-know-about-it/)[ Email Security 18 min Behind the Signature: A Curious Journey into DKIM Implementation Every verified email has an unseen signature that plays a crucial role in establishing trust. Apr 16, 2026 ](/blog/email-security/behind-the-signature-a-curious-journey-into-dkim-implementation/)[ Email Security 9 min 9 Reliable Providers for a Managed outgoing SMTP email server Solution In the fast-moving digital world of today, effective email delivery is essential for businesses that rely on smooth communication and customer interactions. Apr 15, 2026 ](/blog/email-security/9-reliable-providers-for-a-managed-outgoing-smtp-email-server-solution/)[ Email Security 9 min The Signature Checkpoint: DKIM Testing at the Gates of the Inbox As email security continues to advance, the inbox serves as a crucial entry point, with DKIM testing playing an essential role in its protection. Apr 14, 2026 ](/blog/email-security/the-signature-checkpoint-dkim-testing-at-the-gates-of-the-inbox/)[ Announcements 5 min Apple Pay Scam, Crypto Fraud Victims, Retirement Phishing Loss, Cybersecurity News \[April 06, 2026\] Apple Pay Scam, Crypto Fraud Victims, Retirement Phishing Loss, Cybersecurity News \[April 06. Apr 13, 2026 ](/blog/announcements/cyber-security-news-update-week-15-of-2026/)[ DMARC 9 min How ARC resolves email authentication for forwarded messages How ARC resolves email authentication for forwarded messages. Apr 9, 2026 ](/blog/dmarc/how-arc-resolves-email-authentication-for-forwarded-messages/)[ Email Security 9 min Avoiding Burn: How An SPF Generator For Godaddy Can Still Toast Your DMARC If Misused The Sender Policy Framework is deceptively simple: publish a single SPF record as a TXT record in your domain DNS so receiving systems can check whether a. Apr 9, 2026 ](/blog/email-security/avoiding-burn-how-an-spf-generator-for-godaddy-can-still-toast-your-dmarc-if-misused/)[ Email Security 15 min 12 Best Hosted SMTP Servers for High Deliverability in 2026 Selecting the appropriate hosted SMTP server in 2026 is crucial for getting your emails delivered to the inbox rather than the spam folder. Apr 8, 2026 ](/blog/email-security/12-best-hosted-smtp-servers-for-high-deliverability-in-2026/)[ Email Hosting 14 min Inbox Wars: Winning with Powerful SMTP Email Hosting In the bustling digital environment of today, the quest for consumer attention often starts with the inbox. Apr 7, 2026 ](/blog/email-hosting/inbox-wars-winning-with-powerful-smtp-email-hosting/)[ Announcements 5 min LinkedIn Fraud Spike, SIM Scam Bust, UK VIPs Targeted, Cybersecurity News \[March 30, 2026\] LinkedIn Fraud Spike, SIM Scam Bust, UK VIPs Targeted, Cybersecurity News \[March 30. Apr 6, 2026 ](/blog/announcements/cyber-security-news-update-week-14-of-2026/)[ Email Services 9 min 8 Genius Tricks to Master Your DKIM Validator Like a Pro Navigating email authentication can often feel overwhelming, particularly when it comes to DKIM validation and ensuring your emails reach their intended. Apr 2, 2026 ](/blog/email-services/8-genius-tricks-to-master-your-dkim-validator-like-a-pro/)[ Email Security 6 min What happens when your DKIM key is compromised? How can you identify and fix the problem? What happens when your DKIM key is compromised? How can you identify and fix the problem? Apr 2, 2026 ](/blog/email-security/what-happens-when-dkim-key-compromised-and-how-to-fix/)[ Phishing Protection 6 min How Domain Verification Helps Prevent Email Phishing Attacks Email is still the most exploited initial vector of attacks in cybersecurity. Apr 1, 2026 ](/blog/phishing-protection/how-domain-verification-helps-prevent-email-phishing-attacks/)[ Email Services 15 min Set Up A DKIM Key For Microsoft 365 Custom Domains: A Step-By-Step Guide This step-by-step guide explains how to prepare your Microsoft 365 tenant and custom domain to publish a DKIM record. Mar 31, 2026 ](/blog/email-services/set-up-a-dkim-key-for-microsoft-365-custom-domains-a-step-by-step-guide/)[ Email Security 15 min How The Best Anti-Phishing Software Prevents Email-Based Attacks Email-centric threats continue to be a prevalent and expensive cybersecurity challenge for both companies and individuals. Mar 30, 2026 ](/blog/email-security/how-the-best-anti-phishing-software-prevents-email-based-attacks/)[ Announcements 5 min AI Phishing Campaign, TikTok Phishing Targeted, Dutch Police Cyberattack, Cybersecurity News \[March 23, 2026\] AI Phishing Campaign, TikTok Phishing Targeted, Dutch Police Cyberattack, Cybersecurity News \[March 23. Mar 30, 2026 ](/blog/announcements/cyber-security-news-update-week-13-of-2026/)[ DMARC 5 min Why is DMARC important for the retail sector? Why is DMARC important for the retail sector? Mar 27, 2026 ](/blog/dmarc/why-is-dmarc-important-for-the-retail-sector/)[ Announcements 5 min Horabot Resurfaces Mexico, Aura Breach Compromise, Tax Season Threats, Cybersecurity News \[March 16, 2026\] Horabot Resurfaces Mexico, Aura Breach Compromise, Tax Season Threats, Cybersecurity News \[March 16. Mar 23, 2026 ](/blog/announcements/cyber-security-news-update-week-12-of-2026/)[ Email Security 7 min VMC vs CMC explained: Which logo certificate should you choose? VMC vs CMC explained: Which logo certificate should you choose? Mar 19, 2026 ](/blog/email-security/vmc-vs-cmc-explained-which-logo-certificate-should-you-choose/)[ Announcements 4 min Cambodia Targets Cybercriminals, Traditional Security Insufficient, AI Against Phishing, Cybersecurity News \[March 09, 2026\] Cambodia Targets Cybercriminals, Traditional Security Insufficient, AI Against Phishing, Cybersecurity News \[March 09. Mar 16, 2026 ](/blog/announcements/cyber-security-news-update-week-11-of-2026/)[ Email Security 8 min 8 Best Tools To Test DKIM Records And Fix Signature Errors Email authentication is vital for safeguarding your domain against spoofing and enhancing email deliverability. Mar 12, 2026 ](/blog/email-security/8-best-tools-to-test-dkim-records-and-fix-signature-errors/)[ Email Services 16 min Troubleshoot Failed Signatures Using A DNS DKIM Lookup And Record Inspector Email authentication plays a critical role in protecting your domain from spoofing and ensuring that your messages reach recipients’ inboxes. Mar 11, 2026 ](/blog/email-services/troubleshoot-failed-signatures-using-dns-dkim-lookup-and-record-inspector/)[ Email Hosting 18 min 10 Steps To Set Up A Self-Hosted Mail Server Without Hitting Spam Self-hosted email gives you control, privacy, and the flexibility to run open source software instead of relying entirely on a mail service provider. Mar 10, 2026 ](/blog/email-hosting/10-steps-set-up-self-hosted-mail-server-avoid-spam/)[ Cybersecurity 5 min NCSC announces the retirement of Mail Check and Web Check: Here’s what it really means NCSC announces the retirement of Mail Check and Web Check: Here’s what it really means. Mar 10, 2026 ](/blog/cybersecurity/ncsc-mail-check-web-check-retirement-what-it-means/) Showing the 60 most recent posts of **1276** in the archive. The full archive is indexed in [our sitemap](/sitemap-index.xml). Looking for something specific? Try a site search or email [support@duocircle.com](mailto:support@duocircle.com). ```json {"@context":"https://schema.org","@type":"Organization","name":"DuoCircle LLC","url":"https://www.duocircle.com","logo":{"@type":"ImageObject","url":"https://www.duocircle.com/images/duocircle-logo.png"},"description":"DuoCircle is a portfolio of specialized email products covering protection, authentication, delivery, and routing. We deliver about 90% of category-leader capability at roughly half the price, backed by experts who own the outcome. 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