What are email security gateways?

Email security gateways filter messages before reaching user mailboxes. They provide: spam filtering, **malware** detection, **phishing** protection, and data loss prevention. Gateways sit between internet and mail servers, inspecting all traffic.

Functions include: content scanning (attachments, links, text), authentication verification, **sender reputation** checking, encryption enforcement, and policy implementation. Enterprise gateways add: sandboxing, URL rewriting, and advanced threat protection.

Deployment: cloud-based services (**Mimecast**, **Proofpoint**), on-premise appliances (**Barracuda**, Cisco), or integrated with email platforms (**Microsoft Defender** for **Office 365**). Choice depends on infrastructure, compliance needs, and security requirements.