
Explanation:
Group
Notification type
Group1
Message Center Preferences
Group2
Message Center Preferences
The correct answer for both groups is Message Center Preferences. Do not select Organization messages; that option is for sending adoption, onboarding, or product-use messages to users inside Microsoft 365 experiences, not for administrator service-update or maintenance notifications.
For Group1, major service updates are delivered through the Microsoft 365 Message center. Microsoft states that Message center helps admins track upcoming changes, feature updates, and required actions across Microsoft 365 services. Message center preferences can be configured so admins receive email for major updates only.
For Group2, Microsoft 365 planned maintenance events are also handled through Message center, not Service Health alerts. Microsoft's service health documentation is explicit that planned maintenance events are not shown in Service health and should be tracked by staying current with Message center. Microsoft's service continuity documentation also states that customers are notified of planned maintenance through Message center in the Microsoft 365 admin center.
Therefore, select Message Center Preferences for both Group1 and Group2.