Email Filtering

Email filtering is a technological control that analyzes messages for threats. Acting as an inbound email security control for compliance, it automatically blocks spam, phishing attempts, malicious links, and malware attachments before they reach users.

CyberSecure Canada control 5.7.3.8 email filtering explicitly mandates that the organization shall ensure email filtering is implemented. This Level 2 baseline control protects networks from unauthorized access and malicious payloads.

Organizations can implement Microsoft 365 email filtering best practices by configuring Exchange Online Protection and Defender for Office 365. Administrators must enable anti-spam policies, anti-phishing thresholds, and Safe Attachments for robust email malware scanning.

To optimize Google Workspace Gmail email filtering settings, administrators should enable advanced phishing and malware protection within the Google Admin console. This involves configuring safety settings to identify spoofing, block untrusted senders, and sandbox suspicious attachments.

A robust secure email gateway must feature comprehensive inbound email security controls. Key capabilities include email malware scanning for attachments, AI-driven behavioral analysis for phishing detection, and URL filtering to block links pointing to malicious payloads.

Spam filtering targets unsolicited bulk emails to reduce inbox clutter. Phishing protection analyzes sender intent and spoofing to prevent credential theft. Email malware scanning for attachments specifically hunts for viruses, ransomware, and malicious code hidden inside attached files.

While basic filtering meets the minimum standard, implementing URL filtering and time-of-click protection email features is highly recommended. These advanced measures rewrite links and check their safety at the exact moment a user clicks them, thwarting attackers who weaponize links after delivery.

Organizations must establish a secure email quarantine policy and release workflow. Administrators should regularly review quarantined messages, investigate false positives, and ensure users cannot independently release high-risk malware or phishing emails without IT authorization.

To demonstrate compliance during audits, organizations must retain email security logs and reporting. Documentation should track blocked threats, spam volumes, triggered filtering rules, and administrative release actions taken within the secure email gateway. Tools like WatchDog Security's Compliance Center can help centralize these logs and workflow records as evidence, including who reviewed alerts and when.

Organizations should review email filtering rules, allowlists, and blocklists at least annually or when significant changes occur in the threat landscape. Continuous monitoring ensures that the CyberSecure Canada email filtering requirements are consistently met and optimized.

Email filtering evidence can drift because policies change, admins tune thresholds, and logs rotate. Tools like WatchDog Security's Compliance Center can track CSC 5.7.3.8 evidence expectations (filtering policies, quarantine workflow records, and log retention proof), prompt periodic reviews, and flag gaps when required artifacts or approvals are missing.

Even strong filtering won’t catch every campaign, especially business email compromise and highly targeted lures. Tools like WatchDog Security's Phishing Simulation can reinforce the control by measuring click behavior, running vendor-aware scenarios, and producing training evidence that shows users are improving against real-world phishing techniques.