Email security is the combination of policies, processes, and technologies that protect email data from threats, such as phishing or business email compromise (BEC).
Table of Contents
What is Email Security?
Email security is the practice of protecting email systems and data against unauthorised access, malicious use, and accidental exposure.
It covers:
Inbound protection against social engineering attacks
Outbound protection against data loss, misdirected emails, and policy breaches
Identity and access controls for email accounts
Monitoring, investigation, and response to email-based incidents
It typically applies across cloud email (such as Microsoft 365 and Google Workspace), on-premises Exchange, and collaboration platforms that integrate with email.
Key objectives of email security
Especially relevant to businesses who use email as their primary source of communication, effective email security aims to:
Protect confidentiality – ensure only intended recipients can see sensitive content
Protect integrity – prevent tampering with messages, identities, and domains
Maintain availability – keep email services reliable, even under attack
Prove authenticity – confirm that senders, domains, and content can be trusted
Support compliance – meet GDPR, UK Data Protection Act, and sector rules
Reduce human risk – help users spot suspicious messages and avoid mistakes
Why Email Protection Matters
Email is the primary cyber attack vector
As detailed in our recent Email Threat Landscape Report, email remains the number-one initial access vector for cyber attacks. For businesses that use email as their primary channel of communicate for clients and colleagues, it also makes up the primary path for attackers get in.
The frequency of email attacks also continues to rise. Data from Trend Vision One™ Email and Collaboration Security shows that organisations detected and blocked over 57 million high-risk email threats in in 2024, compared to 45 million 2023– a 27% year-on-year increase, even after Microsoft 365 and Google Workspace filtering.
Source: Email Threat Landscape Report —Trend Vision One Email and Collaboration Security Detections after Microsoft 365™ and Google Workspace™
Email threats are also becoming more evasive. Trend telemetry recorded a significant rise in malicious and phishing URLs, including a 20% increase in total malicious and phishing links and a 211% surge in detections from URL sandboxing, driven in part by QR-code phishing (“quishing”) and other dynamic techniques designed to bypass static filters.
Together, these trends confirm that even as organisations improve their defences, email remains the most reliable way for attackers to reach users, test new tactics, and initiate high-impact attacks.
Email threats are costly for businesses
If a email breach happens, consequences for organisations can include:
Direct financial loss from payment diversion and fraud
Ransomware downtime, data theft, and extortion
Legal and regulatory penalties
Loss of customer trust and reputational damage
Increased cyber insurance costs
Trend telemetry shows that the financial stakes around email threats continue to climb. Business email compromise (BEC) incidents increased by 13%, while detections powered by authorship analysis – Trend’s AI-based Writing Style DNA used to spot impersonation fraud – jumped by 77%, indicating a shift towards fewer but higher-value social engineering attacks.
Industry data cited in the report shows that the average attempted wire transfer in BEC attacks reached almost US$129,000 in Q4 2024, nearly double the previous quarter. Combined with the ongoing volume of phishing, malware, and ransomware activity, this underlines how a single missed email can result in six-figure fraud, extended downtime, and long-term reputational damage.
Legal and regulatory context
For UK organisations, email security is tightly linked to governance, risk, and compliance, especially from the following regulations:
GDPR and UK Data Protection Act 2018 – covering personal data breaches
NIS2 Directive and sector regulators – especially for critical infrastructure, healthcare, and finance
ICO reporting – mandatory reporting of qualifying data security incidents
ICO statistics show thousands of data security incidents reported each quarter, with misdirected emails accounting for 12% of all reported breaches—consistently among the most common causes of breaches. This underlines human error in email is a major compliance risk.
Email Security Threats and Risks
Source: Email Threat Landscape Report analysing 2024 email attack data
Phishing and spear phishing
Phishing emails trick users into clicking a malicious link, opening a dangerous attachment, or entering credentials into a fake site. Spear phishing and whaling focus on specific individuals such as executives and finance teams, often using well-researched lures.
There are several different types of phishing, including email phishing, smishing, vishing, and QR code (“quishing”) attacks, many of which use email at some stage of the kill chain.
Like many email-based cyberattacks, phishing activity has been on the rise, with a 20% increase in total phishing URLs in 2024 from the previous year.
Business email compromise (BEC)
In BEC, attackers impersonate executives, suppliers, or partners to trick staff into paying fake invoices or changing bank details – often called payment diversion fraud.
BEC also remains one of the most financially damaging email threats. According to our Email Threat Report, BEC activity recently increased by 13%, while AI-powered authorship analysis detections rose by 77%, showing that impersonation attacks are becoming more targeted and harder to spot by eye.
The same report notes that typical wire transfer amounts in BEC campaigns now average close to US $129,000 (about 1 million GBP) per attempt, again showing how even a single successful email attack can have a material impact on cash flow and business continuity.
Malware and ransomware
Email continues to be a top delivery mechanism for malware and ransomware. Attackers send attachments (for example, Office documents, PDFs, archives) or links that ultimately lead to a malicious download.
While it may seem less common, our research shows that malware delivered through email is evolving rather than disappearing. In 2024, known malware detections via email rose by 47%, even as unknown malware detections dropped by 39%, indicating that attackers are leaning on proven malware families and commoditised tools while defenders rapidly convert “unknowns” into known signatures.
Account takeover and spoofing
If attackers harvest credentials through phishing or brute force, they can log in as a legitimate user and send internal or outward-facing emails that look entirely normal.
Recently, credential theft represents a core driver of account takeover. Overall phishing detections climbed by 31%, while credential phishing surged by 36%, signalling a sustained focus on harvesting login details that can be reused across cloud services, finance tools, and internal systems.
Data loss and misdirected email
Not all email security risks are “external attacks”. Common issues include:
Sending sensitive data to the wrong recipient
Using the wrong email address from auto-complete
Forwarding confidential threads outside the organisation
Emails sent to personal accounts or unauthorised cloud services
ICO data shows misdirected email is one of the top reported causes of data breaches, and recent research suggests it accounts for over a quarter of GDPR data protection incidents globally.
How Email Attacks Work
Most email attacks follow a predictable sequence, even as techniques evolve:
Reconnaissance and targeting – Attackers research targets on LinkedIn, company sites, and social media to understand roles, suppliers, and internal language.
Lure creation – They craft convincing messages that imitate real invoices, approvals, or system notifications, often using AI to refine tone and wording.
Delivery and initial compromise – The email is sent with malicious links, attachments, or QR codes designed to harvest credentials or drop malware.
Establishing persistence – Once a user clicks or opens, attackers may create forwarding rules, install backdoors, or move laterally to other systems.
Action on objectives – Finally, they initiate payment diversion, data theft, ransomware deployment, or further internal phishing from compromised accounts.
However, the tactics often vary depending on what type of email attack is occuring.
How social engineering email attacks work
For social engineering attacks like phishing, email threats still start with reconnaissance and research. Attackers gather information from LinkedIn, company websites, and social media to understand:
Who authorises payments
How suppliers and customers are named
Typical email signatures and tone
Current projects or organisational changes
They then craft tailored messages that reference real people, invoices, or events to appear legitimate.
How malicious email attachments work
Common techniques include:
Links to credential-harvesting sites that mimic Microsoft 365 or banking pages
Attachments that execute scripts, macros, or installers
QR codes in email bodies or attachments that redirect to phishing sites
What happens after an email breach?
Once an attacker has a foothold, they may:
Move laterally into cloud storage, CRM, or finance systems
Exfiltrate sensitive data for extortion or doxing
Deploy ransomware across endpoints and servers
Use the compromised account to launch internal phishing
Email Security Technologies and Controls
Secure email gateways and APIs
Traditional secure email gateways (SEGs) sit in front of mail servers to filter inbound and outbound traffic. Modern cloud email often benefits from API-based protection that integrates directly with Microsoft 365 or Google Workspace to analyse messages before and after delivery.
Trend Micro’s Cloud Email and Collaboration Protection illustrates this model, providing cloud-to-cloud integration, high availability, and protection against phishing, BEC, ransomware, and data loss.
SPF, DKIM, DMARC
To protect identity and domain reputation, organisations should:
Publish SPF records to authorise sending mail servers
Sign messages with DKIM to prove integrity
Enforce DMARC policies to block or quarantine unauthenticated messages
DMARC reports also help security teams see how their domains are being abused in spoofing and phishing campaigns.
Sandboxing and URL analysis
Modern email security technologies use:
Sandboxes to detonate suspicious attachments safely
Time-of-click URL analysis to check links when the user clicks, not just at delivery
Heuristics and reputation data to spot suspicious file types and behaviours
These measures help stop zero-day malware and polymorphic phishing that change content to evade signature-based detection.
Data loss prevention and encryption
Data loss prevention (DLP) policies can:
Detect sensitive data patterns (for example, NI numbers, financial data)
Block or warn users before sending externally
Apply additional checks for large distribution lists or external domains
Email encryption protects confidentiality in transit and at rest, meeting regulatory and contractual requirements when sending personal or highly sensitive information.
AI and behavioural analytics
When protecting email platforms, AI-powered security goes beyond static rules to understand:
Normal communication patterns between users and domains
Abnormal requests such as urgent payment changes or unusual tone
Signs of account compromise (logins from new locations, inbox rules, forwarding)
Trend Micro’s research on AI security combined with email attack data proactive email security emphasises that managing human risk with AI and behavioural analytics is now essential, as attackers themselves weaponise generative AI to make emails more convincing.
Email Security Best Practices for Business
Rather than thinking only about tools, effective email security combines systems that focus on people, process, and technology.
People
Focus on building security-aware behaviour:
Provide regular, role-specific security awareness training
Run realistic phishing simulations and follow up with coaching, not blame
Teach staff to verify unusual financial requests through known channels
Reinforce simple checks: “Does this email make sense? Am I being rushed?”
Encourage users to report suspicious messages quickly to security teams
Process
Define clear, practical processes that users can follow:
Document acceptable use policies for email and collaboration tools
Establish payment and supplier verification steps to reduce BEC and payment diversion fraud, aligned with NCSC guidance
Set rules for sending personal data externally and for using personal email
Build email incidents into your incident response plan, with playbooks for:
Suspected phishing
Confirmed account compromise
Misdirected email or data leakage
Ensure legal, HR, and finance understand their roles in email-related incidents
Technology best practices
Modern email security is as much about architecture as it is about products. Instead of thinking in terms of point solutions and individual vendors, it helps to treat the following capabilities as technology-related best practices that any effective stack should deliver.
Necessary Capabilities:
Advanced phishing and BEC detection (including AI/ML and behavioural analysis)
Protection against ransomware, zero-day malware, and suspicious URLs
Inbound and outbound filtering, DLP, and encryption
Protection for collaboration tools (Teams, SharePoint, OneDrive, Google Drive)
Strong reporting, investigation, and automated response capabilities
Coverage for mobile and remote workers
Email security best practices for small business
Smaller organisations face the same threats but often lack dedicated security teams. Practical steps include:
Turning on built-in security features in Microsoft 365/Google Workspace and enforcing MFA for all staff
Using a reputable email security solution that adds phishing, BEC, and malware protection without complex management
Starting with simple but strict payment verification procedures, especially for bank detail changes
Running lightweight, frequent awareness sessions tailored to non-technical staff
Studies show that smaller businesses can suffer disproportionately high per-employee costs from email breaches and ransomware, making these foundational controls critical.
Email Security Examples: Recent Attacks
Trend Micro’s threat research teams regularly investigate real-world email attacks that illustrate how these threats play out in practice. The following details examples of cyber attacks on email platforms.
BEC payment fraud
One B2B BEC case study shows how attackers compromised a legitimate mail server and quietly monitored conversations between three business partners over several days before inserting a single fraudulent payment request into an existing thread – a textbook example of how patient reconnaissance turns one email into a high-value fraud attempt.
Ransomware via phishing
Recent email threat landscape analysis also documents multiple spear-phishing campaigns that used hijacked threads and weaponised attachments, such as the PikaBot spam wave and operations like Water Makara and Earth Baxia, where attackers embedded obfuscated scripts in ZIP archives to deliver backdoors and steal sensitive information.
In parallel, Trend’s telemetry highlights a broad rise in phishing and credential phishing – 31% and 36% respectively – and a growing reliance on QR-code phishing and other deceptive URL techniques, reinforcing how quickly adversaries adapt to new controls and how important layered, AI-powered email security has become.
Strengthening email security with Trend Micro
Trend Micro’s Email and Collaboration Security is part of a unified, AI-powered platform that protects users, data, and communications across email, collaboration, identity, endpoints, and cloud. In 2024 alone, it discovered and blocked more than 57 million high-risk email threats, on top of what Microsoft 365 and Google Workspace already stopped, demonstrating its impact against phishing, BEC, ransomware, and other advanced email attacks.
To strengthen your email security with proven, multilayered protection, try Trend Vision One™ for free.
Frequently Asked Questions (FAQs)
What is email security?
Email security is the set of policies, processes, and technologies used to protect email accounts, content, and communications from threats such as phishing, BEC, malware, and data loss.
Why is email protection so important for businesses?
Email is still the primary attack vector for cybercriminals, so weak email protection can quickly lead to financial fraud, ransomware, data breaches, and regulatory penalties.
What are the most common email security threats?
The most common email security threats include phishing, spear phishing, business email compromise, malware and ransomware delivery, account takeover, spoofing, and accidental data leaks through misdirected emails.
How do email security technologies help stop attacks?
Email security technologies such as secure email gateways, API-based cloud email protection, sandboxing, URL analysis, DLP, encryption, and AI-driven behavioural analytics work together to detect, block, and contain malicious or risky email activity.
What are email security best practices for business?
Key best practices include enforcing MFA, hardening Microsoft 365 or Google Workspace, implementing SPF/DKIM/DMARC, using advanced email security solutions, training users regularly, and having clear processes for payment verification and incident response.
How can small businesses improve email security without large budgets?
Small businesses can greatly reduce risk by enabling MFA everywhere, using built-in security features in their cloud email platform, adopting a reputable cloud-based email security solution, and implementing simple but strict verification steps for payments and sensitive changes.
How does Trend Micro help with email security?
Trend Micro’s Trend Vision One™ – Email and Collaboration Security provides advanced protection against phishing, BEC, ransomware, and data loss across Microsoft 365, Google Workspace, and collaboration tools, while giving security teams the visibility and automation needed to respond quickly to email-based threats.