Use case: Use this procedure to create a report that shows mailbox and archive sizes, item counts, and deleted item usage across your Microsoft 365 environment. This helps identify large mailboxes and review mailbox storage usage.
About report templates
A report template defines what the report shows (type) and what it targets (scope). Once a template is created, it can be reused to generate new reports or review results from previous runs. The scope of an existing template can be updated at any time, but the type cannot be changed.
To create a report that lists mailbox and archive sizes, do the following:
- Go to Entra ID, right-click Reports, and select New Report Template.
- Enter a name for the report, such as Mailbox Size Report.
- Set the Category to Mailboxes, set the Type to MailboxSize, and click Next.
- Configure the Scope to narrow the report by Department or Country, or leave these fields blank to include all applicable mailboxes.
- Under Mailbox type, select the type of mailbox you want to include:
- Any – Includes all supported mailbox types.
- User Mailbox – Includes user mailboxes.
- Shared Mailbox – Includes shared mailboxes.
- Room Mailbox – Includes room mailboxes.
- Equipment Mailbox – Includes equipment mailboxes.
- Archive Mailbox – Includes archive mailboxes.
- Use Minimum size and Maximum size to limit the report to mailboxes within a specific storage range. For example, set the minimum size to 50 GB to find mailboxes using 50 GB or more.
- Leave Minimum size at 0 GB and Maximum size at Unlimited if you do not want to filter the report by mailbox size.
- Click Create, then click Run to generate the report.
- Once the report completes, double-click it to view and filter the results.
To search and filter the report
- Use the Search field to search across all report columns in real time.
- To filter on a specific column, use
[ColumnName]=[search phrase]. - For column names containing multiple words, omit the spaces. You can shorten a column name as long as you include enough characters to identify it uniquely.
- For example, use
MailboxType=Sharedor the shortermai=shato find shared mailboxes. - Combine searches across multiple columns, e.g.
mai=sha cou=den, to identify shared mailboxes with Country set to Denmark.
To export the report data
- Click Export List… to export all results currently displayed in the report window.
- To copy selected rows instead, select the required rows (CTRL + A to select all), press CTRL + C, and use CTRL + V to paste them into Excel, Notepad, or another tool.
Other Report Types
How to Create a Report: Disabled Users With Microsoft 365 Subscriptions
How to Create a Report: Identify Core Microsoft 365 Workloads Not Being Used
How to Create a Report: Delegated Access to Mailboxes
How to Create a Report: Inactive Users With Microsoft 365 Subscriptions
How to Create a Report: User MFA Configuration and Readiness
