Get a List of Mailboxes a User Has Access to in Exchange/Microsoft 365

To get a list of mailboxes a user has access to in Exchange/Microsoft 365, you can use the following PowerShell command:

Get-MailboxPermission -Identity <mailbox> | where { $_.AccessRights -match "FullAccess" -and $_.IsInherited -eq $false } | Select-Object User,Identity

Replace <mailbox> with the user’s mailbox you want to check. This command will return a list of users who have full access to the specified mailbox, along with the identity of the mailbox.

If you want to get a list of mailboxes a specific user has access to, you can use the following PowerShell command:

Get-Mailbox -ResultSize unlimited | Get-MailboxPermission | where { $_.User -like "<user>" -and $_.AccessRights -match "FullAccess" } | Select-Object Identity

Replace <user> with the user’s name you want to check. This command will return a list of mailboxes that the specified user has full access to.

Exchange Reporter Plus is a comprehensive Exchange auditing and reporting tool that can help you track and audit mailbox access in Microsoft Exchange Server and Microsoft 365 (formerly known as Office 365) environments. Here’s how you can use it to audit mailbox access:

1. Install and configure Exchange Reporter Plus.
2. Log in to the Exchange Reporter Plus web console using your administrator credentials.
3. Navigate to the Auditing tab and select Mailbox Access Auditing.
4. Click on the Add New Policy button to create a new mailbox access audit policy.
5. Give the policy a name and select the mailbox(es) you want to audit.
6. Select the audit actions you want to track, such as successful and/or failed logon attempts, mailbox access by administrators or delegates, and more.
7. Specify the frequency of the audit (daily, weekly, or monthly) and the email addresses of the recipients who will receive the audit reports.
8. Save the policy.
9. You can also generate on-demand audit reports by navigating to the Reports tab and selecting the Mailbox Access Reports category.
10. Select the report type you want to generate, such as Mailbox Access Summary, Mailbox Access by User, or Mailbox Access by Administrator.
11. Configure the report parameters, such as the mailbox(es) and time period you want to include in the report.
12. Click on the Generate Report button to generate the report.

Using Exchange Reporter Plus, you can easily audit mailbox access in your Exchange Server and Microsoft 365 environments, track user activity, and generate comprehensive reports that provide insights into user behavior and system activity.