STEADY DATA
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OLEmail & Communication

How to Check Your Outlook Data Volume

Check mailbox size, quota, folder distribution, and archive scope without reading messages or creating a PST.

Verified against official documentationLast checked October 16, 2026
This is a read-only preliminary check.

Do not export, upload, or send business records. Write down only the approximate storage figures you see.

What this platform may hold

Know what you are measuring.

  • Email and attachments
  • Folders
  • Contacts
  • Calendar items and tasks
Permissions required

Mailbox owner or Microsoft 365 reports reader

Mailbox owners can review their own usage. Organization-wide figures require an authorized Microsoft 365 reporting role.

Start in the source system

Go to outlook.office.com and sign in.

Use the authorized role listed above, then keep this Steady Data guide open beside the portal and follow the visual steps below.

Open Outlook Opens the source system in a new tab. Never share your password with Steady Data.
Official vendor instructions

Want the vendor's full documentation? Open any source below without losing this guide.

Each link opens in a new tab.
Check your data volume

Follow these steps.

Product screens can change. Follow the verified labels and use the linked vendor sources if your layout differs.

01

Open Mailbox storage

Sign in with the authorized role and follow Outlook → File or Settings → Mailbox storage.

OutlookFile or SettingsMailbox storage
Stay in the read-only summary. Do not download, delete, or open individual records.
Outlook · original navigation mapStep 1
Open Mailbox storageExample layout
Search settings and reports
Overview
Mailbox storageChoose this
Users and access
Original Steady Data illustration—not a product screenshot. Labels and navigation are based on the official vendor documentation linked below.
02

Capture the headline volume

Record the mailbox size, quota or available space, and percentage used.

Mailbox storageOverview
Outlook desktop and web use different labels; use the storage or Mailbox Cleanup view available in your version.
Outlook · original navigation mapStep 2
Capture the headline volumeExample layout
Record this figureStorage overviewYour used storage
UsedTotal limit
Original Steady Data illustration—not a product screenshot. Labels and navigation are based on the official vendor documentation linked below.
03

Review the breakdown

Review the folder-size summary for Inbox, Sent, Deleted Items, and any online archive.

Mailbox storageDetails
Aggregate totals are enough for the free valuation. Do not submit raw business records.
Outlook · original navigation mapStep 3
Review the breakdownExample layout
Compare the largest sources
Email or recordsLargest
Files and attachmentsReview
Shared contentReview
Original Steady Data illustration—not a product screenshot. Labels and navigation are based on the official vendor documentation linked below.
04

Record scope and history

Write down the mailbox total, quota, online-archive status, local-PST status, and date checked.

Your worksheetOutlook
Mailbox size covers content retained in the mailbox and its folders. Local archives stored outside Microsoft 365 are not included.
Outlook · original navigation mapStep 4
Record scope and historyExample layout
EmailMailbox usage
FilesStorage used
SitesTotal usage
Write down each service separately
Original Steady Data illustration—not a product screenshot. Labels and navigation are based on the official vendor documentation linked below.
Used vs. limit

Record what is used—not just what is available.

Record mailbox size and quota together. Local PST files and separate online archives sit outside the primary mailbox figure.

Historical coverage

Storage size does not equal record age.

Mailbox size covers content retained in the mailbox and its folders. Local archives stored outside Microsoft 365 are not included.

Troubleshooting

Common reasons your screen may differ.

Mailbox size is unavailable+

Use Outlook on the web or ask for the Exchange mailbox usage report.

An archive is enabled+

Record the online archive separately from the primary mailbox.

Later-stage process

Prepare or export data only after authorization.

Outlook mailbox preparation

After authorization, a mailbox can be exported to PST or handled through an approved Microsoft 365 workflow.

Permissions and safeguardsConfirm mailbox-owner or administrator approval, mailbox and archive scope, and encrypted storage.
1. Outlook desktop2. File3. Open & Export4. Import/Export5. Outlook Data File (.pst)

Typical output: PST for mailbox content; administrative usage reports are commonly CSV.

Official sources

Verify the latest vendor guidance.

These official pages were used to verify this guide. Vendor interfaces and permissions can change.