What it works with
Module: ExchangeOnlineManagement
ExchangeOnlineManagement lets PowerShell connect to and work with Exchange Online.
Context: Exchange Online PowerShell
Compatibility: PowerShell 7 is the supported target for this cloud template.
POWERSHELL / EXCHANGEONLINEMANAGEMENT
FreeBeginnerRead-onlylow
Export mailbox sizes
Exports mailbox sizes and item counts.
Generated locally in your browser · Review before running · Opselith does not connect to your tenant
What this PowerShell script does
Exports mailbox sizes and item counts.
Requirements
- CSV output path - Example: C:\Temp\report.csv
Environment
- Module: ExchangeOnlineManagement
- Permissions: View-Only Recipients
- Output: CSV report
- Context: Exchange Online PowerShell
- Risk: Low
Review before you run The script is generated locally. Test outside production first.
NEXT STEP
Ready to generate
Configure Export mailbox sizes in the Builder, review the generated PowerShell and run it yourself in your own PowerShell session.
More about this script
Why use this template?
Use this free PowerShell script when you need to export mailbox sizes and item counts. It is generated locally and can be reviewed before you run it yourself in your own PowerShell session.
The template uses ExchangeOnlineManagement and requires View-Only Recipients. Output: CSV report. Level: Beginner. Action: Read-only. Risk: Low.
Review before running
The script is generated in your browser. Read it before you run it, and test it outside production first. “Read-only” describes the script itself; anything you add around it can still change data.
Generate the script
- Open the template in the PowerShell Builder.
- Enter the requested values and review the module, permissions, output and risk.
- Generate the script, read it carefully, and test it outside production before use.
The script is generated locally in your browser. Nothing needs to be uploaded to Opselith.
Generate Export mailbox sizes →Before you runModule, permissions, inputs, compatibility and script checks
OPS / SCRIPT DETAILS
Script details
Exports mailbox sizes and item counts. Review these details before generating or running the script.
Generated here. Run by you.Opselith does not connect to your tenant or run PowerShell. After generating, review the script and run it in your own PowerShell session.
Permissions and changes
Permissions: View-Only Recipients
Risk: Low
Read-only: designed to collect information without intentionally changing the target environment.
Changes: Read-only. The script reads data and does not intentionally change the target environment.
Inputs
- CSV output path - Example: C:\Temp\report.csv
What to expect
Output: CSV report
Expect a CSV file at the path you choose. Open it in Excel or another CSV viewer and review the rows.
Example: C:\Temp\report.csvThis template is in the Free library and is generated locally in your browser. Opselith does not run it; you review and run the script in your own PowerShell session.
Example use
Exports mailbox sizes and item counts.
Enter the required values in the Builder, review the generated script and confirm the output before running it.
Before you run: Make sure your account has View-Only Recipients. Check that the ExchangeOnlineManagement PowerShell module is available and that you are using the supported PowerShell version. Review the generated script and output path, then test outside production first.
Script checksWhat has been verifiedQA reviewed
Static checksPassed
PSScriptAnalyzerPending
Real-world run testNot yet recorded
Last checkedNot yet recorded
Real-world run results are shown only after Opselith reviews and accepts a tester report.
Tester: report a result →TEST STATUSWhat Opselith has checked
Last reviewed: 10 Sept 2026
PSScriptAnalyzer: Awaiting a release PSScriptAnalyzer gate that includes this script. No analyzer pass is claimed yet.
Pending or Not yet recorded means there is no accepted result on file yet. A passed analyzer check does not mean the script has been run in a real tenant.
PRACTICAL GUIDE
How to use this result
Use this inventory to compare Exchange Online mailbox size, item count and last-logon statistics without changing mailbox configuration.
When this helps
- Identify large mailboxes for capacity or archive review.
- Create a size baseline before migration or mailbox-cleanup work.
- Spot mailboxes where statistics could not be retrieved and need separate investigation.
How to read the result
- TotalItemSize and ItemCount come from mailbox statistics; LastLogonTime is included when the available statistics cmdlet exposes it.
- Status=ERROR is recorded per mailbox, so a partial CSV must not be mistaken for a complete tenant inventory.
Things to check
- Mailbox statistics can reflect service-side timing and are not a billing or quota decision by themselves.
- Large size or high item count is an operational signal, not proof that content is unnecessary or safe to remove.
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