Exchange Online Protection (EOP) Overview
Understanding the Concept
Exchange Online Protection is the cloud-based filtering service that protects against spam, malware, and other email threats. EOP is included with all Exchange Online plans and processes all inbound and outbound mail.
EOP uses multiple layers of filtering including connection filtering, anti-malware, anti-spam, and anti-phishing policies. The filtering stack processes messages in a specific order, with each layer applying its own verdicts.
The quarantine holds messages flagged by EOP, allowing admins and users to review and release false positives. Quarantine policies define what actions users can take on quarantined messages.
Key Points
EOP Filtering Stack
Connection Filter
IP allow/block lists
Anti-Malware
Scan attachments for malware
Transport Rules
Apply mail flow rules
Anti-Spam
Content filtering & SCL scoring
Why This Matters
EOP is the first line of defense for your email environment. Proper configuration prevents phishing attacks, malware infections, and spam floods while minimizing false positives that block legitimate business email.