June 2025 Microsoft 365 Updates: New Defender SIEM Changes, OneDrive Upgrades, and Feature Retirements

June 2025 brings a wave of significant changes to Microsoft 365 and Defender, impacting organizations, IT administrators, and end users worldwide. From the retirement of legacy security integrations to streamlined file management and mailbox enhancements, these updates reflect Microsoft’s ongoing push toward a more secure, efficient, and user-friendly cloud ecosystem. Here’s a comprehensive breakdown of what’s new, what’s changing, and what’s being retired in these Microsoft 365 updates this month.

Microsoft 365 Updates June 2025

 

Microsoft Defender for Cloud Apps: SIEM Agent Configuration Ends

One of the most critical updates this month is the change to Microsoft Defender for Cloud Apps’ SIEM (Security Information and Event Management) integration. As of June 19, 2025, organizations can no longer configure new SIEM agents within Microsoft Defender for Cloud Apps. This marks the beginning of a phased retirement, with existing agents set to be fully retired between mid-November and late November 2025.

What does this mean for organizations?

• No New SIEM Agents: After June 19, 2025, it is no longer possible to set up new SIEM agents in Defender for Cloud Apps.

• Transition to APIs: Microsoft recommends transitioning to unified APIs for managing activities and alerts data across workloads. These APIs provide enhanced security monitoring, cross-workload visibility, and broader integration options.

• Microsoft Sentinel Support Remains: While SIEM agents are being phased out, Microsoft Sentinel agents will continue to be supported and can still be added.

Action Required:
Organizations using Defender for Cloud Apps SIEM agents should immediately begin planning their migration to the supported APIs and SIEM solutions to ensure continuous access to security data and monitoring capabilities.

OneDrive: Enhanced File Ownership Transfer for Departing Employees

Managing data when employees leave an organization has always been a challenge. In June 2025, Microsoft is rolling out improved OneDrive file ownership transfer features designed to streamline this process.

Key Enhancements:

• Improved Cleanup Emails: Administrators and managers will receive clearer, actionable notifications when an employee departs, making it easier to identify which files need to be transferred or deleted.

• Essential File Filters: New filters help pinpoint critical files that should be retained or reassigned, reducing the risk of data loss.

• “Move and Keep Sharing” Option: This new feature allows files to be transferred to a new owner while maintaining existing sharing permissions, ensuring business continuity and minimizing disruption.

How to Use the Feature:
To transfer ownership, administrators can select files or folders in OneDrive, use the “Manage Access” option, and assign new owners. Although OneDrive does not directly support changing ownership in-place, the process now guides users through sharing, downloading, and re-uploading files to replicate ownership transfer, with improved guidance and automation.

Outlook for Windows: Shared Mailbox Integration Improvements

Microsoft is addressing a longstanding pain point for Outlook users who manage shared mailboxes. Starting in June 2025, those with Full Access permissions can add shared mailboxes as separate accounts in the new Outlook for Windows53. This update brings the following benefits:

• Full Control: Users can manage shared mailboxes with the same flexibility as their personal accounts, including rules, signatures, and settings.

• Seamless Experience: The new integration removes previous limitations, such as shared mailboxes appearing only as extra folders.

• No Admin Action Required: If auto-mapping is enabled, users will see a “Promote” button in their settings to upgrade the mailbox experience.

Rollout Timeline:

• Targeted Release: By end of June 2025

• Worldwide General Availability: By end of August 2025

Feature Retirements: What’s Going Away in June 2025

Microsoft is also retiring several legacy features across the Microsoft 365 suite. Here’s what’s being phased out and what you need to know:

1. OneNote Meeting Details (Windows 10)

• Retirement Date: June 2025

• Impact: The Meeting Details feature will be removed from OneNote for Windows 10. Users must transition to the OneNote for Windows app for continued support and access to new features.

• Action: Encourage users to migrate to the latest OneNote app. iPad and Mac users must upgrade to build 16.95 or later to retain Meeting Details functionality.

2. Viva Engage Private Content Mode

• Retirement Date: June 30, 2025

• Impact: The Private Content Mode in Microsoft Viva Engage will be retired. Verified admins will no longer be able to enable or disable this feature.

• Alternatives: Microsoft recommends using group membership management and eDiscovery tools for content access and compliance needs.

3. Teams Recording Initiator Policy

• Retirement Date: June 30, 2025

• Impact: The MeetingInitiator value and MeetingRecordingOwnership setting in Teams will be eliminated, affecting how recording ownership is tracked and managed.

4. Outlook Interesting Calendar

• Retirement Date: Early June 2025

• Impact: The “Interesting Calendar” feature (also known as Sports Calendar) will be discontinued in Outlook.

Additional Microsoft 365 Changes in June 2025

SharePoint Online: CDN Domain Migration

Microsoft is migrating SharePoint Online to a new CDN (Content Delivery Network) domain in June 2025. This change is designed to improve performance and reliability for content delivery but may require organizations to update firewall rules or allowlists.

Teams: DLP Incident Report Email Changes

Data Loss Prevention (DLP) incident report emails in Microsoft Teams are being updated to provide clearer, more actionable information for administrators and compliance officers.

Exchange: Cmdlet Updates

Exchange is rolling out updates to cmdlets that affect domain reporting and mailbox audit logs, enhancing reporting accuracy and audit capabilities.

What Should Organizations Do Now?

• Review and Communicate: IT administrators should review these changes and communicate them to affected users and teams.

• Plan Migrations: Begin transitioning from deprecated features—especially SIEM agents in Defender for Cloud Apps and Meeting Details in OneNote—to supported solutions.

• Update Training Materials: Ensure that documentation and training reflect the new OneDrive file transfer process, Outlook shared mailbox enhancements, and any retired features.

• Monitor for Additional Updates: Stay tuned for further announcements as Microsoft continues to evolve its cloud offerings.

By retiring outdated features and introducing streamlined workflows, Microsoft is helping organizations adapt to a rapidly changing digital landscape. Proactive planning and communication will be key to ensuring a smooth transition for all users.

For more detailed guidance and official documentation on these Microsoft 365 updates, visit Microsoft’s official update channels and admin message center.