More than 90% of successful cyberattacks start with email, according to the U.S. Cybersecurity and Infrastructure Security Agency (CISA). That’s not because security teams lack tools, but because attackers target human decision-making.
For years, organizations treated email security as a filtering problem: block enough malicious messages, and risk goes down. That assumption no longer holds.
Modern phishing, business email compromise (BEC), and impersonation attacks are designed to bypass technical controls by looking legitimate, arriving at the right moment, and pressuring employees to act quickly.
When email attacks succeed today, it’s rarely because a control failed. It’s because a message reached a person who was persuaded to click, reply, or comply.
That’s why effective email security now goes beyond stopping bad messages. It requires understanding how employees interact with email threats, where risky behaviors emerge, and how organizations reinforce safer decisions in real time.
This guide breaks down practical, proven email security best practices organizations and employees can use to reduce risk by strengthening both technical defenses and the human behaviors attackers rely on most.
Key Takeaways
- Email is still one of the most common starting points for cyberattacks, including phishing, malware delivery, and credential theft.
- Email-based social engineering attacks take advantage of human trust and rushed decisions.
- Strong email security best practices combine authentication, filtering, training, and simple reporting processes.
- Employees reduce risk through everyday actions like verifying senders, handling links carefully, and flagging suspicious messages.
- Human Risk Management helps organizations measure these behaviors and reinforce safer inbox habits.
Why Email Security Still Matters
Email is attackers’ most reliable entry point to organizations because it’s woven into day-to-day work, from invoices to internal requests. High volume and routine use make it easy to exploit human trust and outdated security practices.
The financial consequences of email-based threats can be severe. According to the most recent FBI Internet Crime Report, BEC scams alone led to $2.77 billion in reported losses in 2024.
The threat is only getting worse. Generative AI has made phishing attempts easier to produce, more convincing to read, and harder to detect, raising the bar for defenses that address both technology and user behavior.
What Are the Common Email Security Threats?
Email-based threats come in many forms, but all are designed to bypass technical defenses by manipulating employee behavior. Attackers use familiar-looking messages, fake senders, and urgent requests to get users to click, share credentials, or open dangerous files.
Common email security threats include:
- Phishing attacks: Deceptive emails used to trick users into clicking malicious links or sharing sensitive information.
- Malicious attachments: Seemingly harmless and routine files that install malware or ransomware when opened.
- Credential theft: Messages that send users to fake login pages designed to steal usernames and passwords.
- Business email compromise (BEC): Targeted impersonation scams that pressure employees into sending money, changing payment details, or sharing sensitive information.
- Spoofed domains: Lookalike email addresses or domains used to mimic trusted brands, executives, or business partners.
Email Security Best Practices for Organizations
Effective email security requires more than a single tool or policy. Strong programs combine technical controls that stop threats early with employee-focused reinforcement to reduce the likelihood of human error.
To follow email security best practices, organizations should:
- Use strong email authentication protocols
- Deploy advanced email filtering and anti-phishing tools
- Train employees to recognize phishing and social engineering
- Encourage safe link and attachment handling
- Enable multi-factor authentication (MFA) for email accounts
- Keep email systems and devices updated
- Limit access using the principle of least privilege
- Establish clear policies for email use
- Make reporting suspicious emails easy
- Adopt an integrated approach that combines anti-phishing incident response with cloud email security
Use Strong Email Authentication Protocols
Email authentication protocols help reduce spoofing by verifying that messages claiming to come from your domain are actually legitimate. Common standards include:
- Sender Policy Framework (SPF)
- DomainKeys Identified Mail (DKIM)
- Domain-based Message Authentication Reporting and Conformance (DMARC)
When set up correctly, these protocols make it much harder for attackers to spoof a trusted sender like a CEO or finance leader and pressure an employee into sharing sensitive information or changing payment details.
These controls also strengthen trust in your outbound email and help security teams detect and block fraudulent senders.
Learn must-know email security best practices, including how to reduce phishing risk, protect inboxes, and help employees spot email-based threats.Learn must-know email security best practices, including how to reduce phishing risk, protect inboxes, and help employees spot email-based threats.
Integrated Approach Combining Incident Response with Cloud Email Security
No single control can stop today’s advanced email threats. An integrated approach—combining cloud-native email security with AI-driven, human-vetted anti-phishing incident response—creates a closed-loop defense: detect, report, analyze, remediate and continuously improve. By feeding real-world intelligence back into detection, organizations gain greater visibility, faster response and stronger protection against emerging phishing campaigns.
Deploy Advanced Email Filtering and Anti-Phishing Tools
Filtering is a critical first layer of defense that helps block malicious emails before employees ever see them. Advanced solutions can detect suspicious links, attachments, and impersonation attempts.
Tools like KnowBe4 Defend add adaptive protection by detecting modern phishing attempts that legacy filtering often misses.
Train Employees to Recognize Phishing and Social Engineering
Even the best technical controls won’t catch every threat, which is why employee awareness is just as important. KnowBe4’s security awareness training teaches people to recognize common red flags such as unexpected requests, unusual sender details, or urgent financial instructions.
Over time, regular reinforcement builds safer habits and reduces the chance that social engineering scams succeed.
Encourage Safe Link and Attachment Handling
Real-time coaching through tools like KnowBe4 SecurityCoach helps employees slow down in the moment and make safer decisions when risky activity is detected. Simple behaviors like verifying links before opening them and treating unexpected attachments with caution can prevent credential theft and malware infections.
Enable Multi-Factor Authentication (MFA) for Email Accounts
Multi-factor authentication (MFA) helps prevent attackers from turning stolen passwords into full account access.
If an employee’s credentials are compromised through phishing, MFA requires an additional verification step before an inbox or connected business system can be accessed. This extra safeguard is especially important for high-risk roles such as finance and executive leadership.
Use MFA wherever possible, favoring non-phishable options like hardware or app-based tokens. Avoid SMS-based MFA and always verify authentication requests you didn’t initiate—this alone can block a significant share of credential-theft attacks.
Keep Email Systems and Devices Updated
Attackers often exploit known vulnerabilities in email platforms, browsers, and endpoint software, especially when system patches are delayed. Staying current with updates helps reduce these exposure points and keeps email environments more resilient against evolving threats.
Limit Access Using the Principle of Least Privilege
Email compromises become a lot more damaging when accounts have unnecessary access to sensitive systems or data. Limiting permissions ensures employees only have the access required for their role, containing threats before they spread and reducing the impact of a successful phishing attack.
Establish Clear Policies for Email Use
Employees should have clear guidance on best practices for handling sensitive information over email. Well-defined policies set expectations for data sharing, external communication, and when to escalate suspicious requests.
Solutions like KnowBe4’s Compliance Plus training can reinforce these standards and help employees understand both their security responsibilities and the regulatory requirements that support them.
Make Reporting Suspicious Emails Easy
Fast reporting helps security teams contain threats before they spread. When employees have a simple way to flag suspicious messages, organizations gain earlier visibility into active phishing attempts and emerging patterns.
KnowBe4’s PhishER Plus supports this process by automating email analysis and prioritization, reducing alert fatigue while speeding up response.
Email Security Best Practices for Employees
Even with strong technical controls, employees play a critical role in stopping suspicious emails and impersonation attempts. Organizations should encourage employees to follow these email security best practices:
- Verify senders and be cautious of unexpected emails
- Think before clicking links or opening attachments
- Avoid sharing sensitive information via email
- Use strong passwords and enable MFA when available
- Report suspicious emails promptly
Verify Senders and Be Cautious of Unexpected Emails
Attackers often use familiar-looking emails to appear legitimate, sometimes posing as a manager, vendor, or internal team. Employees should take a moment to review sender details closely, including the email address and tone, especially when a message requests sensitive information, payment changes, or urgent action.
Think Before Clicking Links or Opening Attachments
Phishing emails frequently use links or attachments as the delivery mechanism for credential theft or malware. Before clicking, employees should hover over links to confirm the destination and watch for common warning signs like misspellings, unusual URLs, or unexpected file types. When in doubt, it’s safer to verify the request through another channel than to click quickly.
Avoid Sharing Sensitive Information via Email
Email is not always the right place for sensitive data like passwords, financial details, or customer information. Employees should follow organizational policies for secure data handling and avoid sending confidential information over email unless it’s properly protected and explicitly permitted.
Use Strong Passwords and Enable MFA When AvailableStrong, unique passwords reduce the risk of attackers reusing stolen credentials across multiple accounts. MFA adds another layer of protection by requiring a second form of verification, which can stop account takeovers even if a password is compromised.
Report Suspicious Emails Promptly
Flagging suspicious messages early helps security teams investigate faster, warn others, and remove threats before they spread across inboxes. A single report from one employee can help protect the entire organization from a wider phishing campaign.
The Role of Email Security in a Layered Defense Strategy
Email security is strongest when organizations address not only malicious messages, but also the human behaviors that determine whether those messages succeed.
Human Risk Management (HRM) is a structured approach to reducing the behaviors attackers exploit in email. It goes beyond awareness training to measure patterns like link clicks, responses to social engineering attempts, and reporting activity. This data can then be used for targeted reinforcement and accountability in the areas it’s needed most.
By turning these everyday actions into measurable risk insights, HRM tools like KnowBe4’s HRM+ allow organizations to deliver more relevant training and real-time coaching to reduce the likelihood of compromise and strengthen the human firewall over time.
Strengthen Email Security with KnowBe4
Blocking malicious emails still matters, but it’s no longer enough to protect your organization.
Today’s most effective programs focus on how employees actually interact with email threats: which messages prompt clicks, where risky behaviors surface, and how timely reinforcement can prevent a mistake before it becomes an incident.
KnowBe4 pairs these insights with technical controls, so organizations can shift from filtering messages to actively reducing human risk.
Ready to strengthen email security by reducing human risk? Learn how KnowBe4 helps organizations train employees, detect phishing threats, and stop email-based attacks before they lead to compromise.
