Mail & OneDrive Storage

The Users – Mail & OneDrive Storage report provides an overview of user mailbox and OneDrive storage usage.

The report combines user information with mailbox and OneDrive usage data from Microsoft 365 usage reports. It helps identify unused mailboxes, inactive users with storage, shared mailboxes that may no longer be used, OneDrive storage consumption, and users approaching mailbox or OneDrive quota limits.

The underlying mailbox and OneDrive usage data comes from Microsoft 365 usage reports in the Microsoft admin center. These reports are updated periodically by Microsoft and may not reflect real-time activity. The report therefore includes data update dates in the drilldown table, so you can see when mailbox and OneDrive data was last refreshed.

When to use this report

Use this report to:

• Identify unused or inactive mailboxes

• Find potentially unused shared mailboxes

• Review shared mailboxes with no recent activity

• Find users with high mailbox or OneDrive storage consumption

• Identify users with no mailbox usage data

• Identify users with no OneDrive usage data

• Review inactive users that still have mailbox or OneDrive storage

• Find mailboxes that may be close to quota

• Analyze storage usage by department, company, office, country, manager, or job title

• Support license cleanup, storage cleanup, and lifecycle review

• Validate whether mailbox and OneDrive usage data is up to date

Report overview

The report gives you a high-level view of users, mailbox usage, OneDrive usage, sign-in status, account status, and organizational attributes.

Data freshness

Mailbox and OneDrive usage data is based on Microsoft 365 usage reports.

These reports are updated by Microsoft on a periodic basis and may not reflect changes immediately. For this reason, the report includes update fields in the details table.

Important fields include:

Field	Description
Mailbox data updated	The report refresh date for mailbox usage data
Mailbox last activity	The last known mailbox activity date from Microsoft 365 usage reports
OneDrive data updated	The report refresh date for OneDrive usage data
OneDrive last activity	The last known OneDrive activity date from Microsoft 365 usage reports

Use these fields to confirm whether the usage data is current enough for your investigation.

Focus Table

The Focus Table summarizes the selected storage or activity focus.

The focus can be changed using the Focus Filter.

Available focus options include:

• % Mailbox quota

• Mailbox size

• Mailbox items

• Archive mailbox

• % OneDrive quota

• OneDrive files

• OneDrive size

• F-License fit

• Mailbox last activity

• OneDrive last activity

The Focus Table is designed to quickly answer questions such as:

• How many mailboxes have never been used?

• How many mailboxes have not been active for more than 365 days?

• Which users are close to their mailbox quota?

• How much OneDrive storage is being used?

• Which users have no mailbox data?

• Which users have no OneDrive data?

Mailbox last activity

When Mailbox last activity is selected in the Focus Filter, users are grouped into activity bands.

Typical bands include:

Band	Meaning
No mailbox	No mailbox usage record was found for the user
Never used	A mailbox exists in the usage data, but no activity was found
0–30 days	Mailbox activity was found within the last 30 days
31–90 days	Mailbox activity was found 31 to 90 days ago
91–180 days	Mailbox activity was found 91 to 180 days ago
181–365 days	Mailbox activity was found 181 to 365 days ago
> 365 days	Mailbox activity was more than 365 days ago

This view is useful for identifying mailboxes that may be stale, unused, or candidates for further review.

OneDrive last activity

When OneDrive last activity is selected in the Focus Filter, users are grouped by how recently OneDrive activity was recorded.

This helps identify users with inactive OneDrive storage or users who have OneDrive provisioned but do not appear to use it.

Use this together with OneDrive size and file count to determine whether follow-up is needed.

Common scenarios

Find unused shared mailboxes

Unused shared mailboxes are a common cleanup and governance challenge. Many organizations have shared mailboxes that were created for projects, departments, former roles, support functions, applications, or temporary initiatives, but are no longer actively used.

This report can help identify shared mailboxes that may be unused by combining mailbox activity, mailbox size, mailbox item count, sign-in information, and user or account attributes.

To find potentially unused shared mailboxes:

1. Use the relevant User Purpose or mailbox type filter to focus on shared mailboxes

2. Select Mailbox last activity in the Focus Filter

3. Review the Focus Table for:

   • Never used

   • 181–365 days

   • > 365 days

4. Use the Details Table to review:

   • Mailbox last activity

   • Mailbox used GB

   • Mailbox size GB

   • Mailbox item count

   • Mailbox created date

   • Mailbox data updated

   • Account status

   • Department, company, or owner-related attributes

5. Validate whether the mailbox is still needed before cleanup

Good candidates for review are shared mailboxes that:

• Have no recent mailbox activity

• Have not been used for more than 365 days

• Have very low storage usage

• Have a low mailbox item count

• Have no clear department, owner, or business purpose

• Belong to old projects, functions, or discontinued processes

Recommended action:

Verify ownership and business need before removing, archiving, or converting the mailbox. Also check retention, compliance, and legal hold requirements before deleting mailbox data.

Find unused mailboxes

To find unused mailboxes:

1. Select Mailbox last activity in the Focus Filter

2. Review the Focus Table

3. Select Never used or old activity bands such as > 365 days

4. Review mailbox size, mailbox item count, account status, and user state in the details table

This can help identify mailboxes that may be candidates for cleanup, archiving, or ownership review.

Find inactive users with storage

To find inactive users that may still consume storage:

1. Set User State to Inactive

2. Select Mailbox size or OneDrive size in the Focus Filter

3. Review users with significant storage consumption

4. Check account status, latest sign-in, mailbox last activity, and OneDrive last activity

This is useful when reviewing accounts that may no longer need active licenses or storage.

Find users close to mailbox quota

To identify mailboxes at risk of becoming full:

1. Select % Mailbox quota in the Focus Filter

2. Review the highest quota usage bands

3. Open the details table

4. Check mailbox used GB, mailbox size GB, mailbox item count, and archive status

Users with high mailbox usage may need cleanup, archive mailbox review, retention review, or mailbox quota planning.

Find users with large OneDrive storage

To review large OneDrive usage:

1. Select OneDrive size or % OneDrive quota in the Focus Filter

2. Use the Breakdown Table to group by department, company, manager, or office

3. Review OneDrive used GB, allocated GB, file count, and active file count in the details table

This can help identify departments, users, or processes generating high OneDrive storage consumption.

Find users with no mailbox data

To find users where no mailbox usage record was found:

1. Select Mailbox last activity in the Focus Filter

2. Review the No mailbox category

3. Use the details table to check user purpose, account status, license status, and user source

A user shown as No mailbox means that no mailbox usage record was found for that user in the available Microsoft 365 usage report data.

Find users with no OneDrive data

To find users where no OneDrive usage data was found:

1. Select OneDrive last activity, OneDrive size, or OneDrive files in the Focus Filter

2. Review users with missing or empty OneDrive values

3. Use user state, sign-in status, account status, and license information to understand whether this is expected

A blank OneDrive value or missing OneDrive details means that no matching OneDrive usage data was found for that user in the available Microsoft 365 usage report data.

Validate usage report freshness

To check whether Microsoft 365 usage data is current:

1. Add Mailbox data updated and OneDrive data updated from the Column Selector

2. Review the dates in the details table

3. Use these dates when interpreting mailbox and OneDrive activity

If the data update date is older than expected, remember that the report reflects the latest available usage data from Microsoft 365 usage reports, not necessarily real-time activity.

Recommended workflow

1. Start with the user count and main slicers

2. Use User State, Sign-in Status, Account, and User Source to narrow the scope

3. Select the relevant Focus Filter, such as Mailbox last activity or OneDrive size

4. Use the Focus Table to identify the most important group

5. Use the Breakdown Table to find organizational patterns

6. Use the Details Table to investigate individual users

7. Add or remove fields using the Column Selector

8. Export or follow up on users that require action

Important notes

Mailbox and OneDrive usage data comes from Microsoft 365 usage reports and may be delayed.

A user shown with No mailbox means that no mailbox usage record was found for that user in the available usage report data.

A user shown with Never used means that mailbox data exists, but no mailbox activity was found.

A blank OneDrive value or missing OneDrive details means that no matching OneDrive usage data was found for that user in the available usage report data.

Before taking cleanup actions, validate account ownership, business requirements, retention requirements, and internal lifecycle processes.

For shared mailboxes, always verify ownership, retention, legal hold, business purpose, and whether the mailbox is used by applications, automation, or integrations before deleting or archiving data.