Why Email Remains the Top Cybersecurity Risk for IT Leaders

Email remains the most targeted attack surface for organizations, even as IT leaders deploy advanced defenses.

This first article in our five-part series on modern email security strategies, validates the threat with current data, explores attacker tactics, and provides actionable strategies for reducing risk. Future articles will cover authentication, encryption, and advanced threat protection to help IT leaders strengthen email security from every angle.

Why Email Is Still the Top Risk Vector 

• 91% of cyberattacks begin with email (Verizon DBIR 2024). 
• Business Email Compromise (BEC) losses exceeded $2.9B in 2023. 
• 43% of cyberattacks targeted SMBs last year, proving no organization is immune. 

Despite robust filtering and layered defenses, attackers bypass controls by impersonating trusted domains, vendors, and executives. The real pain point is not just the volume of threats, but the erosion of trust as malicious actors leverage social engineering and AI-driven phishing to target high-value users and critical workflows.

Key Tactics Used by Attackers 

• Impersonation: Attackers mimic executives, vendors, or internal users to trick recipients. 
• AI-driven Phishing: Machine learning is used to craft convincing, targeted messages. 
• Exploitation of Misconfigurations: Gaps in SPF, DKIM, and DMARC allow spoofing and delivery failures. 
• Zero-day Attachments: Malicious files that evade traditional signature-based detection. 

Common Email Attack Vectors and Mitigations 

This table summarizes the most common attack vectors and the technical controls that mitigate them. Use it as a reference for prioritizing your defenses. 

How to Quantify and Prioritize Email Risk 

• Use Microsoft Secure Score to evaluate email-specific controls, including anti-phishing policies and authentication protocols. 
• Supplement with third-party assessments for granular analysis of mail flow, authentication misconfigurations, and exposure to BEC vectors. 
• Track incident response times, user susceptibility rates, and authentication failure trends to measure improvement. 

Actionable Steps for IT Leaders 

• Audit and align SPF, DKIM, DMARC across all domains. 
• Deploy Microsoft Defender for Office 365 for layered protection. 
• Focus on high-risk users, critical domains, and sensitive financial workflows. 
• Schedule regular user awareness training and simulated phishing campaigns. 
• Integrate with SIEM for automated alerting and incident response. 
  

About the Sourcepass Center of Excellence for Microsoft (MCOE) 

The Sourcepass Center of Excellence for Microsoft is a certified Microsoft Solutions Partner. We simplify Microsoft and help IT teams amplify their impact. Through strategy, procurement, implementation, and optimization, we help organizations make confident decisions, modernize faster, and stay aligned with Microsoft’s direction—from hybrid environments to the cloud.