Your system has been infected by malware. Upon investigation, you discover that the malware propagated primarily via email. The malware attacked known vulnerabilities for which patches are…

Encrypting emails at the server protects data confidentiality in transit but does nothing to inspect or block malicious payloads inside the messages themselves.

Scanning and blocking suspect email attachments at the mail server addresses the exact propagation vector identified - email attachments carrying malware. Because this control acts on every inbound message before it reaches any endpoint, it is effective even when patch levels across hosts are unknown, stopping the threat at the point of entry rather than relying on individual host defenses.

A firewall between the email server and the Internet cannot differentiate malicious from legitimate SMTP traffic on port 25, so it will not block malware-laden emails that are delivered through normal mail flow.

Isolating the email server from trusted network segments limits lateral spread after infection but does not prevent employees from opening malicious attachments and getting infected in the first place.