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:
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:
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:
Use the relevant User Purpose or mailbox type filter to focus on shared mailboxes
Select Mailbox last activity in the Focus Filter
Review the Focus Table for:
Never used
181–365 days
> 365 days
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
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:
Select Mailbox last activity in the Focus Filter
Review the Focus Table
Select Never used or old activity bands such as > 365 days
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:
Set User State to Inactive
Select Mailbox size or OneDrive size in the Focus Filter
Review users with significant storage consumption
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:
Select % Mailbox quota in the Focus Filter
Review the highest quota usage bands
Open the details table
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:
Select OneDrive size or % OneDrive quota in the Focus Filter
Use the Breakdown Table to group by department, company, manager, or office
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:
Select Mailbox last activity in the Focus Filter
Review the No mailbox category
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:
Select OneDrive last activity, OneDrive size, or OneDrive files in the Focus Filter
Review users with missing or empty OneDrive values
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:
Add Mailbox data updated and OneDrive data updated from the Column Selector
Review the dates in the details table
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
Start with the user count and main slicers
Use User State, Sign-in Status, Account, and User Source to narrow the scope
Select the relevant Focus Filter, such as Mailbox last activity or OneDrive size
Use the Focus Table to identify the most important group
Use the Breakdown Table to find organizational patterns
Use the Details Table to investigate individual users
Add or remove fields using the Column Selector
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.
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