With over 20 years protecting enterprise inboxes and inspecting 1.8 billion emails every day, Mimecast knows what works.
You'll gain valuable insights to strengthen your organization's email security posture that can be put into action today.
Email security defined
Email security includes the tools, protocols, and strategies enterprises deploy to protect their email communications from unauthorized access, loss, and compromise. At its core, email security aims to prevent phishing scams, block malicious software distribution, stop email spoofing attempts, and prevent sensitive data exfiltration - all while maintaining legitimate business communication flow.
Today's advanced email threats have evolved far beyond simple spam emails. Security teams now defend against sophisticated, multi-layered cyberattacks that blend technical exploits with psychological manipulation. Emerging email threats leveraging AI now include deepfake impersonations, polymorphic phishing that constantly changes to evade detection, and synthetic identities that build trust before striking.
Why is email security important?
Email remains the primary communication channel for enterprises, with the average office worker sending and receiving 121 emails daily through their email service. This massive volume, multiplied across thousands of end users, creates an expansive attack surface that cybercriminals actively exploit. Understanding the benefits of email security helps justify investment and prioritize protection strategies.
The enterprise email attack surface
Modern enterprises operate complex email ecosystems that extend far beyond simple inbox-to-inbox communication. Email integrates with cloud-based email applications, connects to customer relationship management systems, and flows through multiple endpoints - from corporate laptops to personal smartphones.
Volume creates vulnerability: A 5,000-employee organization processes approximately 605,000 emails daily. Even with 99.9% accuracy in threat detection, 605 potentially malicious emails could reach inboxes every day. This mathematical reality demonstrates why layered security approaches are essential.
Department-specific email security risks: Different departments face unique challenges. Finance teams receive invoice fraud attempts targeting bank accounts, HR departments get resume-based malware, and executives face targeted spear-phishing campaigns. Each requires tailored protection strategies while maintaining unified security policies.
Cloud application integration: Email accounts serve as authentication gateways to countless SaaS applications. Account compromise through a single email can cascade into breaches across Microsoft 365, Salesforce, Slack, and other critical business tools. This interconnectedness amplifies the impact of successful email attacks.
Financial and reputational impact
Email security breaches carry devastating consequences that extend beyond immediate financial losses. Organizations must consider both direct costs and long-term reputational damage.
Direct financial costs: The average cost of a data breach reached $4.88 million in 2024, according to IBM's Cost of a Data Breach Report. Email-initiated breaches typically involve higher costs due to their ability to gain access to multiple systems and expose sensitive customer data.
Business disruption: Ransomware attacks delivered via email can paralyze operations for days or weeks. Manufacturing companies have been reported to experience costs of $1.9M per day of downtime. Service providers face similar productivity losses plus potential service level agreement (SLA) penalties.
Reputational damage: Customer trust, once broken, takes years to rebuild. After email-based breaches, organizations typically experience some level of customer churn rates and struggle to acquire new business. Public companies often see immediate stock price impacts, with average drops of 7% following breach announcements.
Compliance and regulatory requirements
Email security is legally mandated across numerous industries and jurisdictions. Regulatory frameworks impose specific requirements for email protection, retention, and privacy.
General Data Protection Regulation (GDPR) requires organizations processing EU citizen personal data to implement appropriate technical measures protecting information in emails. Violations can result in fines up to 4% of global annual revenue or €20 million, whichever is higher. Organizations must use encryption and access controls for GDPR compliance.
Health Insurance Portability and Accountability Act (HIPAA) mandates healthcare organizations use encryption for patient information in emails. HIPAA violations range from $140 to over $2 million per incident, depending on negligence levels. Email archiving systems must maintain audit trails for six years.
Financial Industry Regulatory Authority (FINRA) requires financial services firms to archive all business communications in tamper-proof repositories with instant search capabilities. These systems must provide chain-of-custody documentation for litigation and regulatory audits.
Sarbanes-Oxley Act (SOX) requires public companies to preserve email communications related to financial reporting. Email archiving solutions must ensure tamper-proof storage and rapid retrieval capabilities for auditor requests. Non-compliance can result in criminal charges for executives.
Additional frameworks like the Cybersecurity Maturity Model Certification (CMMC) for government contractors add layers of complexity. Organizations often juggle multiple overlapping mandates, making policy-based encryption and automated compliance essential.
The convergence of operational risks, financial impacts, and regulatory requirements makes email security a boardroom-level concern. Organizations that view email security as merely an IT issue risk catastrophic breaches that threaten their very existence.
The different types of email threats
Email threats have evolved into a sophisticated ecosystem of attack vectors, each designed to exploit specific vulnerabilities in technology, processes, or human behavior. Security teams must understand these distinct threat categories to build effective defense strategies that address each attack method's unique characteristics.
Phishing and spear-phishing attacks
Phishing attacks cast wide nets, sending identical malicious emails to thousands of recipients hoping to trick victims into revealing credentials or downloading malware. These campaigns typically impersonate trusted brands like Microsoft, Amazon, or major banks. Phishing emails often create urgency with subject lines like "Account Suspended" or "Immediate Action Required" to bypass critical thinking.
Spear-phishing represents phishing's targeted evolution. Attackers research specific individuals, crafting personalized messages that reference real projects, colleagues, or recent activities. This personalization dramatically increases success rates - spear-phishing campaigns have been found to have a 53% average click rate.
Whale phishing exclusively targets C-suite executives. These attacks often involve weeks of reconnaissance, studying executive communication patterns, travel schedules, and business relationships. Attackers might wait until a CEO is traveling internationally before launching an attack, knowing the executive will be distracted and more likely to make quick decisions.
QR code phishing (quishing): Attackers embed malicious QR codes in email content, directing mobile devices to credential-harvesting sites. Since many email security tools can't scan QR code content, these attacks bypass traditional URL filtering.
Malware and ransomware distribution
Traditional attachment-based malware hides malicious code within seemingly legitimate files. Common formats include macro-enabled Office documents, PDF files with embedded JavaScript, and compressed archives containing executables. Modern variants use password-protected ZIP files to evade scanning, including the password in the email body.
Fileless malware represents the next evolution in email-borne threats. These attacks leverage legitimate system tools like PowerShell or Windows Management Instrumentation (WMI) to execute malicious commands directly in memory. Since no malicious files touch the disk, traditional antivirus solutions often miss these attacks entirely.
Ransomware delivery via email typically follows a multi-stage process. Initial emails contain downloaders that retrieve the actual ransomware payload from command-and-control servers. This staged approach helps evade detection and allows attackers to deploy different ransomware variants based on the victim's environment. Once executed, these attacks have the power to paralyze entire organizations within hours.
Impersonation and spoofing techniques
Impersonation attacks exploit trust relationships, manipulating technical protocols and human psychology simultaneously.
Social engineering and Business Email Compromise (BEC) remain the costliest email threats. BEC attacks alone caused $2.9 billion in losses in 2023, according to the FBI's Internet Crime Report. These attacks leverage compromised credentials to impersonate executives or vendors. Attackers study communication patterns, then send fraudulent wire transfer requests or redirect invoice payments.
Domain spoofing manipulates email headers to display fake sender addresses. Attackers might send emails appearing to originate from "ceo@yourcompany.com" even though they control no company infrastructure. While authentication protocols like Sender Policy Framework (SPF) and DomainKeys Identified Mail (DKIM) can prevent exact domain spoofing, attackers adapt with lookalike domains.
Lookalike domain attacks register domains with subtle variations, replacing "m" with "rn" or using internationalized characters that appear identical to Latin letters. An email from "arnazon.com" or "microsoƒt.com" can fool even vigilant users, especially on mobile devices where fonts are smaller.
Display name spoofing exploits email clients that prominently show sender names while hiding actual email addresses. Attackers create free webmail accounts but set display names to match executives or trusted channel partners. Users see "John Smith, CEO" without noticing the actual IP address is "totallynotascam@freemail.com."
Credential harvesting and account takeover
Credential harvesting techniques have grown increasingly sophisticated. Modern phishing sites perfectly mirror legitimate login pages, often using valid Secure Sockets Layer (SSL) certificates to display the reassuring padlock icon. These sites capture not just strong passwords but also two-factor authentication codes in real-time, immediately using them to access victim accounts.
Account Takeover (ATO) extends beyond initial compromise. Attackers establish persistence through mail forwarding rules, OAuth token abuse, or backup email modifications. They monitor communications for weeks, learning about pending deals, payment schedules, and organizational hierarchies before striking.
Advanced attack tactics
Modern email threats increasingly leverage sophisticated psychological manipulation and emerging technologies, with generative AI enabling attackers to craft highly personalized, grammatically perfect phishing emails at scale that mimic writing styles and reference real projects, making detection and response significantly harder.
Deepfake audio integration represents an emerging threat where attackers follow email compromises with voice calls using AI-generated executive voices. After receiving an urgent email from the "CEO," victims receive a follow-up call with a convincingly cloned voice confirming the request. This multi-channel approach significantly increases attack success rates.
Payloadless phishing eliminates traditional indicators like attachments or embedded links. Instead, these emails can use legitimate services like Google Forms, Microsoft Forms, or DocuSign to harvest credentials. Since these services have positive reputations, some security tools can miss them.
Thread hijacking hacks email accounts to reply to existing conversation threads. Victims receive malicious responses within real ongoing discussions, dramatically lowering suspicion. Attackers access email histories, understand context, and craft believable responses that fit naturally into conversations.
Understanding these diverse threat categories enables security teams to implement targeted defenses addressing each attack vector's unique characteristics.
The next section explores specific technologies and strategies for building comprehensive email security programs.
How to prevent email attacks
Preventing email attacks requires a layered defense strategy that combines multiple security technologies, each addressing different threat vectors and attack stages. No single solution can stop all threats. Effective email security demands defense-in-depth approaches that protect at the gateway, endpoint, and user levels simultaneously.
Implement a layered defense strategy
Layered email security operates like a medieval castle's defenses. It has multiple barriers that attackers must overcome, with each layer catching threats the previous one missed. Modern email security architectures typically deploy five to seven distinct protective layers, reducing successful attacks to near-zero levels.
Defense-in-depth benefits: When organizations implement proper layering, gateway filters might block 95% of threats, AI analysis catches 80% of the remainder, sandboxing stops 90% of what gets through, and user training prevents 75% of final attempts. Combined, these layers reduce risk by 99.99% - improving email from vulnerability to manageable risk.
Layer integration requirements: Effective layering requires security controls that share threat intelligence and coordinate responses. When sandboxing identifies new malware, that signature should immediately update gateway filters. When users report suspicious emails, those indicators should enhance AI training models. This integration multiplies each layer's effectiveness.
Deploy gateway-level protection
Email gateways serve as the first line of defense, processing every message before it reaches user inboxes.
Secure Email Gateways (SEGs) inspect all inbound and outbound email traffic, applying multiple detection techniques at once. Modern SEGs block known spam sources through IP reputation filtering, analyze message headers for spoofing indicators, and scan content for malicious URLs or attachments. Leading solutions like Mimecast can process over a billion emails a day while maintaining 99% accuracy rates.
Advanced Threat Protection (ATP) enhances traditional gateway filtering with sophisticated detection capabilities. ATP solutions decrypt and inspect encrypted attachments, rewrite URLs for time-of-click analysis, and convert potentially dangerous file types to safe formats. These systems particularly excel at catching zero-day threats that signature-based systems miss.
Domain‑based Message Authentication, Reporting & Conformance (DMARC) enforcement at the gateway level prevents domain spoofing by verifying sender authenticity. Organizations implementing strict DMARC policies with gateway enforcement report big reductions in impersonation attacks. Gateway DMARC processing checks SPF alignment, validates DKIM signatures, and applies policy decisions before messages reach internal systems.
Utilize AI-powered threat analysisArtificial intelligence enhances email security from reactive blocking to predictive prevention.
Machine learning models analyze millions of email attributes to identify threats that rule-based systems miss. These models examine writing patterns, sender behavior, communication graphs, and content anomalies. They're great tools to significantly reduce false positives.
Natural Language Processing (NLP) understands email context and intent, catching social engineering attempts that lack traditional indicators. NLP engines identify unusual urgency, emotional manipulation, and impersonation attempts by comparing messages against baseline communication patterns. They excel at detecting BEC attacks where technical indicators are absent.
Behavioral AI learns normal communication patterns for each user, flagging anomalies that suggest compromise or attack. When a user suddenly emails unusual recipients, requests wire transfers for the first time, or sends messages at odd hours, behavioral AI generates alerts. This approach catches insider threats and compromised accounts that other defenses miss.
Enable sandboxing and dynamic analysis
Sandboxing provides safe environments for detonating suspicious content without risking production systems.
File sandboxing executes attachments in isolated virtual machines, monitoring for malicious behavior. Modern sandboxes detect evasion techniques like delayed execution, environment checking, and human interaction requirements. They run files through multiple operating systems and application versions, ensuring comprehensive coverage.
URL sandboxing follows links through multiple redirects, analyzing destination sites for phishing indicators or malware downloads. Time-of-click protection re-scans URLs when users access them, catching websites that turn malicious after initial delivery. Advanced systems render pages in isolated browsers, protecting against zero-day browser exploits.
Sandbox evasion detection identifies malware attempting to detect virtualized environments. Modern sandboxes use bare-metal systems, randomize environmental indicators, and simulate user behavior to trigger evasion-resistant malware. They also employ extended analysis periods, catching malware that delays execution.
Secure outbound email
Protecting outbound email prevents data loss and stops compromised accounts from launching attacks.
Data Loss Prevention (DLP) scans outgoing messages for sensitive information like credit card numbers, social security numbers, or confidential documents. Policy-based DLP automatically encrypts, blocks, or redirects messages containing protected data. Modern DLP uses machine learning to identify sensitive content even when users attempt to disguise it.
Outbound email scanning prevents compromised accounts from sending malware or phishing emails to partners and customers. These systems detect unusual sending patterns, bulk recipient lists, and suspicious content. When threats are detected, accounts are automatically suspended pending investigation.
Email encryption protects sensitive communications through automatic policy-based encryption. Messages containing financial data, health information, or intellectual property are encrypted based on content, recipient domain, or user selection. Modern solutions provide seamless encryption that doesn't impede business workflows.
Conduct security awareness training
Human-focused defenses address the reality that technical controls can't stop every threat.
Simulated phishing campaigns test employee susceptibility while providing immediate training opportunities. Organizations running monthly simulations report much higher reductions in click rates within six months. Effective training programs customize difficulty based on user roles and past performance, gradually increasing sophistication.
Role-based training tailors security education to specific job functions and risk levels. Finance teams receive focused training on invoice fraud and wire transfer scams. Executives get specialized sessions on whale phishing and board member impersonation. IT staff learn advanced threat indicators and response procedures.
Microlearning approaches deliver bite-sized training modules that maintain engagement without disrupting productivity. Two-minute weekly videos, interactive quizzes, and real-world scenario discussions achieve higher retention than annual training marathons.
Provide real-time user warnings
Just-in-time interventions catch threats that reach inboxes despite other defenses.
Warning banners alert users to suspicious message characteristics before they interact with content. Effective banners highlight specific risks like external senders, similar domain names, or unusual requests. Color-coded severity levels help users quickly assess risk without banner fatigue.
Interactive warnings require user acknowledgment before accessing suspicious content. Pop-ups that ask "This sender has never emailed you before. Are you expecting this message?" can greatly reduce impulsive clicks. Smart warnings learn from user feedback, reducing false positives over time.
Contextual guidance provides specific advice based on detected threats. Instead of generic "be careful" messages, contextual warnings explain "This message asks for wire transfer approval but comes from an unverified sender. Always verify payment requests through a phone call." This specificity dramatically improves user compliance.
Combining these preventive measures creates resilient email security programs that adapt to evolving threats while maintaining business productivity. The key lies not in any single technology, but in thoughtful integration of multiple defenses that protect technology, processes, and people simultaneously.
Strengthening email security through human-centric approaches
Human-centric email security recognizes that employees represent both the greatest vulnerability and the strongest defense against email threats. By strengthening users from potential victims into active security participants, organizations can dramatically improve their overall data security while building a culture of cyber awareness.
Mimecast's Human Risk Management (HRM) Platform
Mimecast's Human Risk Management (HRM) platform combines behavioral analytics, targeted simulations, and adaptive training to address the human element of email security. The platform continuously analyzes user interactions with email threats, identifying high-risk individuals and behaviors that require intervention.
Behavioral data analysis tracks how users interact with emails, measuring risk indicators like clicking suspicious links, downloading unexpected attachments, or responding to unusual requests. The platform assigns dynamic risk scores to each user based on their behavior patterns, role criticality, and exposure to targeted attacks. Users with elevated risk scores receive additional security controls and focused training interventions.
Adaptive simulation campaigns test user susceptibility with increasingly sophisticated phishing simulations tailored to individual risk profiles. Rather than one-size-fits-all testing, the platform adjusts simulation difficulty based on user performance, job role, and past behavior. Finance team members might receive invoice fraud simulations, while executives face whale phishing attempts that mirror real threats targeting their positions.
Personalized training pathways deliver education modules specifically addressing each user's vulnerabilities and knowledge gaps. When a user falls for a simulated phishing attack, they immediately receive targeted microlearning content explaining the specific indicators they missed. This just-in-time training achieves three times higher retention rates compared to annual security awareness programs.
Developing users with Mimecast Engage
Mimecast Engage transforms security awareness from a compliance checkbox to an engaging experience in which users actually want to participate. The platform gamifies security education while providing practical skills users can instantly apply.
Active threat participation gives users the ability to become part of the security team rather than passive targets. Engage provides real-time threat intelligence relevant to each user's role, showing them actual attacks targeting their department or industry.
Risk score transparency shows users their personal security risk scores and provides clear actions to improve. Users can see how their clicking behavior, reporting rates, and training completion affect their scores. This transparency can lead to measurable improvements in behavior over time.
Email security technology and tools
Email security technology has evolved from simple spam filters to sophisticated ecosystems that leverage artificial intelligence, behavioral analytics, and cloud-native architectures. Modern organizations now require comprehensive toolsets that address threats at multiple layers while maintaining seamless user experiences and operational efficiency.
Core email security solution categories
Today's email security landscape encompasses distinct solution categories, each addressing specific threat vectors and operational requirements.
Secure Email Gateways (SEGs) form the foundation of enterprise email security, processing all inbound and outbound messages through comprehensive inspection engines. Modern SEGs combine signature-based detection, reputation filtering, and content analysis to block 99% of commodity threats before they reach mail servers.
Cloud-native email filters operate directly within cloud email platforms like Microsoft 365 and Google Workspace, providing inline protection without routing changes. These solutions leverage API integrations to scan messages after delivery but before user access, catching threats that bypass native platform security. Cloud-native filters excel at detecting internal threats and compromised account activities that traditional gateways miss.
Domain Name System (DNS)-based protection prevents email threats at the network level by blocking communication with malicious domains. These solutions maintain real-time databases of compromised domains, phishing sites, and command-and-control servers. By filtering DNS queries, they stop malware callbacks and credential theft even if malicious emails reach inboxes.
Email archiving solutions capture and preserve all email communications for compliance, legal discovery, and security investigations. Modern archiving platforms provide instant search across massive data volumes, automated retention policies, and tamper-proof storage. Security teams leverage archives to investigate incidents, trace attack patterns, and recover from ransomware by restoring clean email data.
Advanced detection technologies
Machine learning and behavioral analysis have significantly improved email threat detection, catching sophisticated attacks that evade traditional defenses.
Machine learning threat detection analyzes millions of email attributes to identify malicious patterns without relying on signatures. These systems examine sender reputation, message structure, linguistic patterns, and embedded content to calculate risk scores.
Behavioral analysis engines establish baselines for normal communication patterns, then flag anomalies suggesting compromise or attack. These systems track metrics like typical recipients, sending times, language patterns, and content types for each user.
Computer vision for image-based threats addresses the growing trend of attacks using screenshots or images to evade text-based filters. These systems use optical character recognition (OCR) and image analysis to detect phishing URLs, malicious QR codes, and branded impersonation attempts hidden in images. Advanced implementations can identify subtle logo modifications used in brand spoofing attacks.
Natural Language Processing (NLP) understands email context and intent, detecting social engineering attempts that lack technical indicators. NLP engines identify emotional manipulation, unusual urgency, and impersonation attempts by analyzing writing style, tone, and semantic meaning. They excel at catching business email compromise attacks where technical indicators are absent.
Integrated security ecosystems
Modern email security requires integrated platforms rather than disconnected point solutions, with tools sharing intelligence and coordinating responses.
API-driven integration connects email security tools with broader security ecosystems including Security Information and Event Management (SIEM), Security Orchestration, Automation and Response (SOAR), and endpoint protection platforms. When email security detects a threat, it automatically shares indicators with other security tools, enabling coordinated response. This integration reduces mean time to respond (MTTR) from hours to minutes.
Threat intelligence sharing leverages global visibility to protect all customers from emerging threats. When one organization encounters a new attack, threat signatures immediately propagate to protect the entire customer base. Leading platforms process billions of emails daily, providing unmatched visibility into threat evolution.
Automated response orchestration coordinates actions across multiple security layers when threats are detected. Automated playbooks might simultaneously quarantine emails, disable compromised accounts, block malicious domains, and notify security teams. This orchestration prevents attack spread while minimizing manual intervention.
Mimecast's comprehensive email security platform
Mimecast's ecosystem exemplifies modern integrated email security, combining multiple protection layers with centralized management and intelligence sharing.
Mimecast Advanced Email Security serves as the platform's core, providing multi-layered inspection of all email traffic. The solution employs AI-powered, multi-layered detection that moves beyond traditional signature-based methods for evolving threats. Its cloud architecture scales automatically, handling traffic spikes during targeted campaigns without performance degradation.
Our DMARC Analyzer simplifies email authentication deployment, helping organizations prevent domain spoofing and improve deliverability. The tool provides visual reports showing which services send email on the organization's behalf, identifies unauthorized senders, and guides DMARC policy implementation.
Mimecast Incydr provides comprehensive insider risk management and data protection across endpoints, browsers, and cloud environments. The solution addresses critical threats like employee-driven data leaks and Shadow AI risks, where 86% of security leaders express concern about data exfiltration. Its intelligent PRISM system prioritizes risks while automated response controls correct mistakes, block unacceptable activities, and contain insider threats - all deploying in minutes without impacting productivity.
Deployment and management considerations
Successful email security technology deployment requires careful planning and ongoing optimization.
Hybrid deployment models combine on-premises and cloud components to meet specific regulatory or architectural requirements. Organizations might maintain on-premises gateways for data sovereignty while leveraging cloud-based threat intelligence and sandboxing. This flexibility ensures security without compromising compliance requirements.
Performance optimization ensures security measures don't impact user productivity or email delivery times. Modern platforms use techniques like parallel processing, intelligent caching, and regional deployments to maintain sub-second processing times. Regular performance tuning based on traffic patterns ensures consistent user experiences.
Continuous improvement processes adapt security configurations as threats evolve and business needs change. Security teams should review detection rates, false positive trends, and user feedback monthly, adjusting policies accordingly.
Email security best practices and implementation
Implementing effective email security requires more than deploying technology. It demands comprehensive policies, proper configuration, and organization-wide commitment. Security teams must balance protection with usability while ensuring all stakeholders understand their roles in maintaining email security.
Critical Actions for Email Security
- Enforce multi-factor authentication (MFA) on all email accounts
- Deploy SPF, DKIM, and DMARC authentication
- Configure strict domain filtering
- Implement role-based access controls (RBAC)
- Run monthly phishing simulations
- Deploy AI-powered threat detection
- Enable email sandboxing
- Establish one-click threat reporting
- Implement data loss prevention (DLP)
- Create email retention and archiving policies
- Monitor email traffic with centralized dashboards
- Review security metrics weekly
- Update incident response playbooks quarterly
- Conduct annual third-party security assessments
- Automate threat intelligence integration
Secure your email, protect your business
Email remains cybercriminals' favorite attack vector, but layered defenses combining advanced technology, authentication protocols, and human-centric training can transform it from vulnerability to strength. With threats evolving daily - from AI-powered phishing to sophisticated impersonation - organizations need comprehensive protection that adapts as quickly as attackers do.
Ready to upgrade your email security from vulnerability to strength? Discover why 43,000 organizations trust Mimecast to protect their most critical communication channel.
