Guides
Common PCI DSS Email Security Audit Findings And How To Avoid Them
Learn the most common PCI DSS email security audit findings and discover practical steps to avoid compliance issues, protect data and strengthen email security.
Blog
Email security, in plain English.
Practical guidance on SPF, DKIM, DMARC, BIMI, phishing protection, and the parts of email infrastructure that quietly break things. Written by the DuoCircle team for people who run email and want to stop getting paged.
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Announcements (381) Email Security (303) Phishing Protection (151) DMARC (127) Email Services (77) Email Hosting (50) Data Privacy (38) Outbound SMTP (26)
Tutorials
7 Steps To Verify ARC Seals Using Popular Email Header Analysis Tools
Learn 7 simple steps to verify ARC seals using popular email header analysis tools to validate authentication chains and improve email deliverability.
News
Ecopetrol Theft, Lidl Vendor Incident, Patch Tuesday – Cyber News
Stay ahead of cyber threats with this week's top security news, from ransomware and data breaches to zero-days, plus why SPF, DKIM, and DMARC remain essential.
Intermediate
Proven Methods for Corporate Email Cybersecurity Setup
Strengthen corporate email cybersecurity with SPF, DKIM, DMARC, TLS, and monitoring to prevent spoofing, improve deliverability, and protect your brand.
Foundational
How Microsoft 365 Accounts Become Targets For Credential Harvesting Attacks
Learn how Microsoft 365 accounts become targets for credential harvesting attacks, common tactics used by cybercriminals, and best practices to stay protected.
Advanced
9 SMTP Authentication Hardening Techniques To Protect Mail Servers From Abuse
Strengthen email security with these 9 SMTP authentication hardening techniques to protect mail servers from abuse, spam, phishing, and unauthorized access.
Foundational
What Is Ping Spoofing? Understanding How It Works and How to Prevent It
Learn what ping spoofing is, how attackers use ICMP spoofing, the risks it creates, and practical steps to detect and prevent network security threats.
Intermediate
Common Email Throttling Mistakes That Lead to Deferred or Rejected Emails
Avoid common email throttling mistakes that cause deferred or rejected emails. Learn proven strategies to improve email deliverability and sending success.
News
Accenture Breach, AssuranceAmerica Exposed, Mount Royal – Cyber News
Weekly cybersecurity roundup: Accenture breach, AssuranceAmerica leak, AI ransomware, Edge flaw, ShareFile alert, and key email security updates.
Guides
Public Folder Migration Checklist For Microsoft 365 And Exchange Online
Follow this Public Folder Migration Checklist for Microsoft 365 and Exchange Online to ensure secure, seamless migration with minimal downtime and data loss.
Foundational
What Is an ARP Spoofing Attack? Understanding the Risks and How to Defend Your Network
Learn what ARP spoofing attacks are, how they work, the risks they pose, and proven strategies to prevent network traffic interception and data theft.
Comparisons
15 Email Uptime Monitoring Features To Look For In 2026
Discover the 15 essential email uptime monitoring features to look for in 2026 to prevent outages, improve email security, and ensure reliable email delivery.
Phishing Protection 7 min
Hackers Are Taking Over Microsoft 365 Accounts Without Stealing a Password
A new phishing wave takes over Microsoft 365 accounts without ever stealing a password, and it slips past MFA and standard URL scanning. Here is how the device code trick works and the layered defense that stops it.
Foundational
How GDPR Email Compliance Affects Marketing, Consent, And Data Privacy
Learn how GDPR email compliance impacts marketing, consent, and data privacy while improving transparency, trust, and lawful email communication practices.
News
Aflac Japan Breach, HSIN Attack, Foxconn Ransomware – Cyber News
Stay updated on this week's top cybersecurity news, including major data breaches, ransomware attacks, exploited flaws, AI threats, and email security risks.
Intermediate
12 Ways To Maintain Email Deliverability After Completing Email Warm-Up
Learn 12 proven ways to maintain email deliverability after completing email warm-up, improve inbox placement, protect sender reputation, and boost engagement.
Guides
How to Configure SPF for Get A Newsletter: A Complete Setup Guide
Configure SPF for Get A Newsletter with this step-by-step guide. Learn how to publish, verify, and optimize your SPF record for better email security.
Tutorials
How To Perform An Email Blacklist Check Before Sending Large Campaigns
Check your email domain and IP against major blacklists before large campaigns to improve deliverability, avoid spam filters, and protect sender reputation.
Intermediate
10 Email Retention Strategies For Managing High-Volume Mailboxes
Discover 10 email retention strategies for managing high-volume mailboxes, improving compliance, reducing storage costs, and strengthening email security.
Intermediate
We Are Open-Sourcing Commando.io: Server Automation Meets the LLM Era
DuoCircle is winding down the hosted Commando.io service and open-sourcing the code. Here is why we think pairing webhook-driven server recipes with an LLM is worth building in the open.
News
Tata Ransomware, Bajaj Attack, Fortinet Compromised – Cyber News
Weekly cybersecurity roundup: Tata & Bajaj ransomware, Fortinet credential breach, Linux kernel flaws, malware takedowns, global cyber threats and FIFA risks 2026
Foundational
5 Best AI Note Takers for Sales Calls in 2026
Discover the 5 best AI note takers for sales calls in 2026. Compare features, pricing, CRM integrations, and automation to boost sales productivity.
Advanced
How To Build An Email Infrastructure Monitoring Dashboard That Actually Prevents Outages
Build an email infrastructure monitoring dashboard that detects delivery issues, tracks SMTP health, and provides real-time alerts to prevent costly outages
Guides
How to Configure DKIM for Squarespace to Improve Email Security and Deliverability
Learn how to configure DKIM for Squarespace to improve email security, prevent spoofing, boost deliverability, and strengthen SPF and DMARC authentication.
Tutorials
How To Add A DKIM Record (V=DKIM1) In 5 Simple Steps
Learn how to add a DKIM record (v=DKIM1) in 5 simple steps. Improve email authentication, prevent spoofing, and boost email deliverability.
Advanced
DKIM For Multi-Tenant SaaS: Email Authentication Best Practices
Learn DKIM deployment best practices for multi-tenant SaaS platforms. Improve email security, prevent spoofing, and ensure trusted email authentication.
News
ShinyHunters Hits Kodak, One Medical Breach – Cyber News
Cybersecurity News June 2026: ShinyHunters targets Kodak and One Medical, Operation Endgame disrupts SocGholish, and critical flaws impact major platforms.
Comparisons
12 Best DMARC Reporting Solutions That Provide Actionable Email Authentication Insights
Discover the 12 best DMARC reporting solutions that deliver actionable email authentication insights, helping improve security, visibility, and compliance.
Tutorials
How to Configure SPF for Network Solutions (NetSol)
Learn how to configure SPF for Network Solutions, authorize sending servers, prevent email spoofing, and improve email deliverability with proper SPF setup.
Intermediate
How To Verify DMARC Records For Multiple Domains From A Single Dashboard
Verify DMARC records across multiple domains from a single dashboard, simplify monitoring, improve email security, and ensure policy compliance efficiently.
Intermediate
15 Email Migration Service Features That Matter Most for Growing Businesses
Discover 15 essential email migration service features that ensure secure data transfer, minimal downtime, compliance, scalability, and business growth.
News
Oracle Zero-Day, VPN Alert, ServiceNow Denies Breach – Cyber News
Stay informed on the latest cyber threats, including Oracle zero-days, VPN exploits, ransomware attacks, data breaches, and phishing scams.
Advanced
Mail Server Authentication Strategies For High-Volume Email Senders
Learn effective Mail Server Authentication strategies for high-volume email senders to improve deliverability, prevent spoofing, and strengthen email security.
Guides
Pros and Cons of Tenant-to-Tenant Email Migrations in Regulated Industries
Explore the pros, cons, and compliance risks of Microsoft 365 tenant to tenant migrations. Learn how teams in regulated industries can protect data integrity.
Intermediate
How to Configure SPF, DKIM, and DMARC for Amazon SES
Learn how to configure SPF, DKIM, and DMARC for Amazon SES to improve email security, prevent spoofing, and boost email deliverability.
Guides
How to Strengthen Outbound SMTP for Fintech Firms to Safeguard Customer Emails
Struggling to protect customer emails? Discover how modern SMTP for fintech secures against phishing, enhances deliverability, and safeguards sensitive data.
Advanced
10 DKIM Key Rotation Checklist Mistakes That Break Email Deliverability
Avoid these 10 DKIM key rotation checklist mistakes that weaken email security, break authentication, and damage email deliverability rates.
Intermediate
SPF Include Mechanism Explained: Balancing Deliverability, Security, And Scalability
Learn how SPF include mechanisms improve email deliverability, strengthen email security, and support scalable SPF record management.
News
DentaQuest Leak, Cisco Patch Pending, Instagram Bug – Cyber News
Stay updated with the latest cybersecurity news: DentaQuest breach, Cisco zero-day, Instagram bug, supply chain attacks, and emerging cyber threats.
Intermediate
Preventing SPF Configuration Errors: 11 Recommendations For MSPs
Prevent SPF configuration errors with these 11 MSP recommendations to improve email authentication, boost deliverability, and strengthen domain security
Intermediate
SQL Injection Prevention: Essential Strategies for Securing Modern Applications
Protect your web applications from SQL injection attacks with proven prevention strategies, secure coding practices, input validation, and layered defenses.
Advanced
Office 365 Migration: Security Risks To Avoid With Sensitive Data
Avoid costly security risks during an Office 365 migration solution. Protect sensitive business data with best practices for secure migration.
Intermediate
10 DKIM Authentication Testing Reports Every Security Team Should Review
Review 10 essential DKIM authentication testing reports that help security teams identify misconfigurations, improve deliverability, and stop spoofing.
News
FBI Warns Firms, Carnival Breach, GlobalProtect Flaw – Cyber News
Cybersecurity News: FBI warns of Silent Ransom attacks, Carnival confirms 6M-record breach, GlobalProtect exploits surge, and AI-powered threats grow.
Intermediate
DNS Vulnerabilities: Major Threats, Risks, and How to Reduce Exposure
Learn about major DNS vulnerabilities, security risks, and proven ways to reduce exposure, prevent attacks, and strengthen your domain protection.
Intermediate
How To Verify Sender Policy Framework Compliance Using SPF Lookup Tools
Verify Sender Policy Framework compliance using SPF lookup tools to identify record issues, improve email authentication, and enhance deliverability.
Intermediate
15 SPF Record Validation Mistakes That Cause Email Delivery Failures
Avoid these 15 SPF record validation mistakes that can trigger email delivery failures, authentication issues, spam filtering, and domain reputation damage.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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