Strengthening Email Security with Microsoft Defender and AppRiver

Email remains the primary entry point for cyberattacks, including phishing, ransomware, and business email compromise (BEC). As threats continue to evolve in sophistication, organisations must move beyond single-layer security and adopt a defence-in-depth strategy. 

At Dolphin IT Solutions, we take a proactive approach to protecting our clients by combining Microsoft Defender for Office 365 with AppRiver Email Security (now part of OpenText Cybersecurity). This layered model strengthens protection, improves resilience, and ensures a more secure email environment. 

Our approach is part of our broader commitment to delivering reliable IT support and cybersecurity services designed to safeguard modern businesses. 

Why Layered Email Security Matters 

Relying on a single email security solution introduces unnecessary risk. Even advanced platforms can occasionally miss emerging or highly targeted threats. 

A layered approach ensures: 

• Multiple detection layers across the email flow 
• Redundancy if one system fails to detect a threat 
• Enhanced protection against zero-day attacks 
• Reduced likelihood of successful phishing or credential compromise 

This strategy aligns with industry best practices and modern frameworks such as Zero Trust. 

Microsoft Defender for Office 365: Intelligent Native Protection 

Microsoft Defender for Office 365 provides advanced, AI-driven threat protection directly within the Microsoft 365 ecosystem. 

Key capabilities include: 

• Safe Attachments: Sandboxing email attachments to detect malicious behaviour 
• Safe Links: Real-time scanning of URLs at the time of click 
• Anti-Phishing & Anti-Spoofing: Machine learning detection of impersonation attempts 
• Automated Investigation & Response (AIR): Rapid threat remediation 
• Global threat intelligence powered by Microsoft security signals 

Defender excels at detecting sophisticated attacks, including advanced persistent threats (APTs) and offers post-delivery protection, ensuring threats are neutralised even after reaching users. 

AppRiver (OpenText): Perimeter Email Security and Continuity 

AppRiver, now part of OpenText Cybersecurity, acts as a frontline email gateway, filtering threats before they enter your Microsoft 365 environment. 

Their Email Threat Protection solution provides comprehensive protection against phishing, ransomware, spoofing, and business email compromise attacks.  

Core features include: 

• Advanced spam and malware filtering at the perimeter 
• Real-time detection using behavioural and reputation analysis 
• Email encryption for secure communications 
• Business continuity services to maintain access during outages 
• Protection against inbound, outbound, and internal email threats 

By stopping the majority of malicious emails before they enter your environment, AppRiver significantly reduces exposure and improves overall system performance. 

Better Together: A Multi-Layered Defence Strategy 

Combining Microsoft Defender and AppRiver creates a powerful multi-layered security architecture: 

Key Benefits: 

• Increased detection rates 
• Reduced risk of phishing and BEC attacks 
• Protection against zero-day vulnerabilities 
• Improved email system resilience and uptime 
• Enhanced security visibility for IT teams 

This layered approach ensures that even if a threat bypasses one layer, it is highly likely to be caught by the other. 

Business Benefits for Your Organisation 

Implementing a layered email security model delivers tangible outcomes: 

• Significant reduction in spam and malicious email traffic 
• Improved detection of targeted and advanced phishing campaigns 
• Lower risk of data breaches and credential compromise 
• Increased user confidence in email communications 
• Stronger compliance with cybersecurity standards 

These improvements not only strengthen security but also enhance operational efficiency. 

Future-Proofing Your Email Security Strategy 

Cyber threats continue to evolve rapidly, with attackers leveraging automation and AI to launch more convincing and targeted campaigns. 

By adopting a layered approach with Microsoft Defender and AppRiver, organisations can better defend against: 

• Advanced phishing attacks 
• AI-driven cyber threats 
• Supply chain email compromise 
• Business email fraud 

This ensures your organisation remains protected both today and in the future. 

Strengthen Your Email Security Today 

A single layer of email protection is no longer sufficient. A layered email security strategy provides the resilience and intelligence needed to defend against modern threats. 

If your organisation is reviewing its email security posture, we can help you design and implement the right solution. 

Contact our team today to discuss how we can secure your Microsoft 365 environment.