Top email security issues every organization should consider

Roughly 80% of data breaches begin right in an employee’s inbox. Why? Because it’s cheap, fast and bypasses your expensive firewalls by targeting human psychology instead of system vulnerabilities.

Email security issues have evolved far beyond simple spam. We’re now fighting AI-generated phishing, targeted credential theft and ransomware delivery systems that traditional filters can’t catch. The FBI confirmed that phishing was the No. 1 cybercrime in 2024, costing victims tens of millions.  

Email is the central hub of trust, habit and high-value data — invoices, passwords, approvals and collaboration all live there, making it a perfect target. As a result, understanding common email security threats is no longer optional for IT and security managers. Awareness is the first step toward effective email security. Your defense strategy must now be built on AI-driven detection, automated response, deep integration with your cloud ecosystems (like Microsoft 365) and clear visibility into what’s happening. To stay ahead of evolving threats, IT and security leaders need clarity on where the risks lie since knowing the enemy is half the battle.

Let’s take a look at the most significant email security issues organizations face, and how to build a layered, strategic defense to mitigate them.

1. Phishing and spear phishing

Phishing is still the undisputed king of common email security threats. Attackers send deceptive messages that appear legitimate, mimicking trusted brands like Microsoft or even internal IT alerts, to steal login credentials, financial data or internal documents.

Phishing messages are one of the most common entry points for ransomware attacks, especially when they capture credentials or deliver remote-access tools that pave the way for later compromise. Once inside, threat actors escalate privileges, harvest domain credentials and schedule simultaneous encryption across multiple systems to overwhelm recovery efforts.  

But spear phishing is what keeps security managers up at night. Attackers research your team on LinkedIn, craft personalized subject lines and even mimic internal communication styles to build credibility. Increasingly, phishing kits use AI-generated text and voice cloning to make scams indistinguishable from reality. 

2. Business email compromise (BEC)

Business email compromise (BEC) is where the real financial damage happens. Forget malware; these attackers use your own organizational chart against you. They impersonate your CEO, a trusted vendor or an HR partner and craft convincing high-pressure emails designed to trick employees into wiring hundreds of thousands of dollars or sending the entire employee W-2 database.

The average BEC incident costs over $120,000, according to the FBI’s Internet Crime Report, and global damages exceed $2.9 billion annually. 

3. Account takeover (ATO)

Account takeover (ATO) is an insidious threat because the attacker is inside your house. After stealing valid credentials, often from a third-party breach, they gain access to a legitimate corporate account. Once inside, they send internal phishing messages, intercept invoices and exfiltrate data, all from a trusted, legitimate account that bypasses your filters.

This form of account takeover is notoriously hard to detect. According to Barracuda’s 2025 Email Threats Report, 20% of organizations experience an ATO attempt each month.

4. Data loss and insider threats 

Accidental data loss is rampant — employees might send confidential spreadsheets to personal accounts, attach the wrong file or forward client data without encryption. Meanwhile, insider threats — deliberate data theft by disgruntled or departing staff — can be just as damaging. 

5. Spam and malware flooding

It’s tempting to dismiss spam as a solved problem from 2005, but according to Barracuda’s 2025 Email Threats Report, 25% of global email traffic is malicious or unwanted spam. Attackers use mass-mailing bots to distribute Trojans, adware and phishing links, hoping one evades detection. The real danger lies in volume and “alert fatigue.” When your team is flooded with junk, they are more likely to overlook a truly dangerous email. 

6. Misconfigured security policies 

Misconfigured security policies are a leading cause of email security breaches. Common errors include missing authentication records, overly permissive allow-lists and disabled phishing filters. Misconfigurations are often introduced during cloud migrations, when default settings override hardened policies.

Nearly half of all domains still lack an enforced Domain-based Message Authentication, Reporting and Conformance (DMARC) policy, leaving them wide open to spoofing. This is a critical failure. Regular configuration reviews, especially after system updates, are crucial. Don’t assume your cloud defaults are secure. They rarely are.

7. Lack of user awareness and training

You can buy the best security stack on the market, but it can all be defeated by one employee making one bad click. Over 95% of breaches tied to common email security threats trace back to human error — not a sophisticated zero-day, but an employee who couldn’t spot a fake login page. The hard truth is, your team is not as prepared as you think. 

Organizations can dramatically reduce phishing and ransomware risks by adopting a proactive, layered defense. Here are the nonnegotiable email security best practices:

• Adopt defense-in-depth: No single control is perfect. Combine a secure email gateway to block mass threats, inbox-level AI detection for sophisticated phishing and ongoing training as your human firewall. If one layer fails, another catches it.
• Implement authentication (SPF, DKIM, DMARC): The “Big Three” of email authentication. Sender Policy Framework (SPF) lists valid senders, DomainKeys Identified Mail (DKIM) signs messages, and DMARC enforces policy. Start in monitor mode but aim for p=reject. An unenforced policy is merely advice.
• Enforce multifactor authentication (MFA): MFA is the simplest way to block ATO. Move away from SMS codes — vulnerable to SIM swapping — and prioritize authenticator apps or hardware keys for administrators.
• Conduct ongoing awareness training: A compliance checkbox doesn’t build habits. Simulate real phishing, test user response and coach high-risk employees with short, contextual refreshers. Integrate in-the-moment prompts before users click.
• Back up and segment critical data: Assume compromise. Maintain offline, immutable backups (the 3-2-1 rule: three copies, two media, one off-site). Conduct restore-from-backup tests quarterly. Segment networks so attackers can’t encrypt everything.
• Automate incident response: The faster you remove a threat, the smaller the impact. Automation can quarantine malicious messages enterprise-wide and revoke session tokens instantly — cutting mean time to response from hours to seconds.
• Review and patch regularly: Attackers exploit unpatched systems. Establish monthly patch cadences and confirm deployment across mail servers and clients.
• Monitor emerging threats: Stay connected to Cybersecurity and Infrastructure Security Agency (CISA), Information Sharing and Analysis Centers (ISACs) and vendor threat feeds to track new common email security threats. Early intel lets you preempt campaigns targeting executives or industries.

After reading that list of threats, you’re probably thinking about the half-dozen different point solutions you’d need to manage it all. That’s where a unified platform becomes essential. Instead of juggling multiple vendors and disjointed policies, Barracuda Email Protection integrates all these layers into a single pane of glass.

It’s an AI-powered platform designed to combine threat detection, data protection and user education in one ecosystem.

Key capabilities include: 

• Spam, Malware and Advanced Threat Protection: Stops spam, malware and advanced threats using layered heuristics and sandboxing before they hit your inbox.
• Account Takeover Protection: Monitors for unusual sign-in patterns, impossible travel or suspicious IP activity — and automatically isolates compromised accounts to prevent lateral movement.
• Incident Response: Streamlines detection-to-remediation workflows by quarantining malicious emails, blocking senders and enabling quick rollback of unauthorized changes.
• Security Awareness Training: Builds employee resilience through ongoing, adaptive simulations and education.

Barracuda Email Security exemplifies how AI and automation can strengthen this posture without adding complexity, turning email from an organizational weak point into a protected, compliant communication channel. 

Don't wait for a breach to test your defenses; start your free trial of Barracuda Email Protection today. Not sure what you need yet? Find the right solution with the Email Protection Configurator.