EOP is a service that is integrated in Office 365.

This system was created to protect the Exchange system, and it holds the responsibility of protecting, filtering, and ensuring the hygiene of your email, as an outer layer before messages hit the end user's inbox.

Because it operates at an outer level, before the core of Exchange is reached, it constitutes a powerful protection that mitigates several risks. This system was created as a distributed computational system, across all Microsoft data centers, to have the ability to scan, protect, and deliver the legitimate email in the fastest possible way.