Permission & Access Issues

How to Safely Access a Microsoft 365 User Mailbox as an Administrator

Huma Ashraf Ch Oct 1, 2026 868 views

Question details

Administrators require a secure and compliant method to access a specific user's Microsoft 365 mailbox for investigation purposes or after the employee has left the company.

How to Safely Access a Microsoft 365 User Mailbox as an Administrator

Product: Microsoft 365
Device & OS: not provided
Scenario: An IT administrator needs to review or manage the email account of an employee who has departed or is under investigation without compromising security protocols.
Observed behavior: To maintain security, compliance, and accurate audit trails, the administrator must access the mailbox contents without requesting the user's password or bypassing multifactor authentication (MFA).

Before you start

Ensure you are logged in with an account that has Global Administrator or Exchange Administrator privileges in your Microsoft 365 tenant.

Solution 1Recommended

Assign Full Access Permission in Exchange Admin Center

The most secure and compliant method is to delegate Full Access permissions to your administrator account, bypassing the need for password sharing.

By utilizing the Exchange admin center to assign permissions, you maintain strict adherence to corporate security policies. This prevents the unauthorized sharing of user credentials and multifactor authentication methods.

Log in to Exchange admin center

Navigate to the Microsoft 365 admin center and open the Exchange admin center using your administrator credentials.

Navigate to Mailboxes

In the left-hand navigation menu, click on 'Recipients' and then select 'Mailboxes'.

Select the target user

Find and click on the mailbox of the user you need to investigate or manage to open their properties panel.

Access Delegation settings

In the user's mailbox settings pane, click on the 'Delegation' tab.

Assign Full Access

Under the 'Full Access' section, click the edit or add button, and assign your administrator account to grant yourself the necessary viewing permissions.

Best Practice: Using delegation ensures that all actions taken within the mailbox are properly logged in the Microsoft 365 compliance audit trails under your admin account name.

Solution 2

Open the Delegated Mailbox in Outlook on the Web

Once Full Access permissions are configured, you can seamlessly open the user's mailbox directly from your own web-based Outlook session.

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Frequently Asked Questions

Why shouldn't I just ask the user for their Microsoft 365 password?

Sharing passwords and MFA methods compromises account security, violates most IT compliance policies, and breaks the audit trail. By using delegation, actions are logged correctly under the administrator's account rather than the user's account.

Can I assign Full Access permissions using PowerShell instead of the admin center?

Yes, administrators can use the Add-MailboxPermission cmdlet in Exchange Online PowerShell to quickly grant Full Access to a user's mailbox via the command line.

Will the user be notified when an administrator accesses their mailbox?

By default, Microsoft 365 does not send an email alert to the user when an admin assigns Full Access or opens their mailbox. However, these administrative actions are recorded in the unified audit log for compliance review.

Does Full Access allow me to send emails as the user?

No, Full Access only allows you to open, view, and manage the mailbox items. If you need to send emails that appear to come from the user, you must also assign 'Send As' or 'Send on Behalf' permissions in the Exchange admin center.

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