Attachment blocking is a mail security control that stops selected file types from being delivered through email. Administrators use it to block risky or unnecessary formats, such as script files, archives, or application packages, before they reach users’ inboxes. The goal is simple: reduce the chance that a dangerous file can be opened, executed, or forwarded inside the organization.
This control matters because email is one of the most common paths for malware delivery and social engineering. Attackers often rely on users trusting an attachment and launching it manually, so removing high-risk file types shrinks the attack surface. In defense, attachment blocking is usually combined with spam filtering, sandboxing, and policy rules that allow safer delivery methods instead. It does not prove a file is malicious; it prevents delivery based on type, which makes it a preventive layer rather than a detection tool.