Account Security Problems

How to Investigate a High-Severity Alert for Added Mailbox Delegate Permission

Maira Mehtab Sep 28, 2026 869 views

Question details

The user needs to investigate a high-severity alert triggered by newly added delegate access to a mailbox to determine if it is authorized or a security breach.

How to Investigate a High-Severity Alert for Added Mailbox Delegate Permission

Product: Workspace Security / Email Admin
Device & OS: not provided
Scenario: Responding to an administrative high-severity security alert regarding newly assigned mailbox permissions.
Observed behavior: A high-severity alert is generated when delegate access is newly added to a mailbox, which could indicate a legitimate administrative change or unauthorized access by a compromised account.

Before you start

Ensure you have administrative privileges to access email audit logs, security centers, and mailbox permission settings before beginning your investigation.

Solution 1Recommended

Investigate and Resolve the Mailbox Delegate Alert

Follow a systematic approach to review audit logs, verify authorization, and remediate unauthorized changes to secure the mailbox.

Investigating this alert requires analyzing who made the change, when it occurred, and whether the mailbox owner or IT department approved the request. Timely action is critical to prevent potential data breaches.

Review Alert Details

Open the security alert dashboard and analyze the payload to identify the affected mailbox, the delegate account added, and the exact timestamp of the event.

Check Audit Logs

Access your administration or compliance center to review the audit logs. Identify the specific administrator account that executed the permission modification.

Confirm Authorization

Contact the mailbox owner and the IT team to verify if the delegate access was officially requested and approved through your organization's ticketing system.

Remediate Unauthorized Access

If the change is confirmed as unauthorized, navigate to the affected user's mailbox settings and immediately remove the unapproved delegate permissions.

Investigate Sign-In Activity

Check the recent sign-in logs for both the mailbox owner and the administrator who made the change to identify any suspicious logins or compromised accounts.

Investigate and Resolve the Mailbox Delegate Alert

Incident Response: If the permission assignment is confirmed as unauthorized, promptly follow your organization's formal incident-response process, which may include resetting passwords and revoking active sessions.

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Frequently Asked Questions

What is mailbox delegate permission?

Mailbox delegate permission allows one user to manage another user's mailbox. Depending on the exact rights granted, the delegate can read, send, and delete emails on behalf of the original mailbox owner.

Why does adding a delegate trigger a high-severity alert?

Granting delegate access provides extensive control over a mailbox. If done maliciously by an attacker, they could steal sensitive data, intercept communications, or send phishing emails internally, making it a critical security risk that requires immediate review.

How can I prevent unauthorized mailbox delegation?

Implement Multi-Factor Authentication (MFA) for all administrator accounts, enforce strict Role-Based Access Control (RBAC) to limit who can modify mailbox settings, and regularly audit permissions to minimize the risk of unauthorized changes.

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