If you manage Exchange Online for an E3 tenant, you are getting more bang for your buck. Microsoft has started rolling out Defender for Office 365 (MDO) Plan 1 to Microsoft 365 E3/G3 and Office 365 E3/G3 licenses, with completion expected by August 2026. This doesn’t requiere any purchase, or separate provisioning, it just show up automatically for licensed users as the rollout reaches your tenant.

What you had vs. what you’re getting

Up to now, E3 mailboxes were protected by Exchange Online Protection (EOP) — spam filtering, basic anti-malware, and standard anti-phishing. That’s table stakes, and it stays in place.