How to Export an Office 365 Mailbox to PST (2026)

How to Export an Office 365 Mailbox to PST

To export an Office 365 (Microsoft 365) mailbox to PST in 2026, you use eDiscovery in the Microsoft Purview portal: create a search scoped to the mailbox, run an export with "Create PSTs for messages" selected, and download the package from Process manager in your browser. The old routes many guides still describe - the classic Content Search interface, the ClickOnce eDiscovery Export Tool, and the New-ComplianceSearchAction -Export PowerShell command - have all been retired by Microsoft. This guide covers the current supported methods, verified against Microsoft's documentation, and then an honest look at whether a PST is actually the right destination for what you are trying to keep.

Method 1: Export a Mailbox to PST with Purview eDiscovery

This is the supported, licence-included path for admins. You need an account with eDiscovery permissions (eDiscovery Manager role or equivalent) and a Microsoft 365 E3 or E5 licence assigned to the exporting user.

1. Open the Purview portal. Go to purview.microsoft.com and sign in with an account that holds eDiscovery permissions.
2. Create a case and a search. Select the eDiscovery solution card, create (or open) a case, then on the Searches tab create a search. Scope the data source to the mailbox you want - the search picker can include departed users' mailboxes, and Microsoft's export options even include a specific setting for "All people and groups" to include departed users.
3. Add conditions if needed. Leave the query empty to capture the entire mailbox, or add date ranges and keywords to narrow it.
4. Run the export. Open the search, select Export, name it, and under Export format choose Create PSTs for messages. Two options worth knowing: "Organize data from different locations into separate folders or PSTs" gives you one PST per mailbox, and the primary mailbox plus any archive mailbox are merged into a single PST automatically.
5. Download from Process manager. When the export completes, download the packages directly in the browser from the Process manager page - no export tool installation. Use an up-to-date browser, allow pop-ups for the Purview portal, and unzip with 7-Zip or similar rather than the built-in Windows extractor.

Three caveats Microsoft documents that catch admins out:

• Export packages expire after 14 days and are permanently deleted - download promptly.
• Very large exports auto-cancel after seven days of processing - split big mailtenancies into date-range batches.
• Maximum PST package size is configurable (1, 2, 5, or 10 GB) - large mailboxes arrive as multiple PSTs.

Method 2: PowerShell - What Still Works and What Was Retired

Many older guides show a full PowerShell export pipeline ending in New-ComplianceSearchAction -SearchName "..." -Export. That no longer works: Microsoft retired the -Export (and -Report) parameters on 26 May 2025.

What still works in Security & Compliance PowerShell:

New-ComplianceSearch -Name "Departed user - jsmith" -ExchangeLocation jsmith@yourdomain.com
Start-ComplianceSearch -Identity "Departed user - jsmith"

You can script the search creation and execution - but the export itself must then be run from the Purview portal as in Method 1. The only fully programmatic export path is the Microsoft Graph eDiscovery API, which requires eDiscovery (Premium) - an E5-level capability. For most tenants, "script the search, click the export" is the practical reality.

Method 3: Export from Outlook (Small, One-Off Cases)

For a single small mailbox you still have access to, classic Outlook for Windows can export directly: File, Open & Export, Import/Export, "Export to a file", Outlook Data File (.pst). This also works for a shared mailbox the signed-in user has full-access rights to.

Two limitations: the new Outlook client has no PST export - you need classic Outlook - and this method requires the mailbox to still be signed-in and accessible, which usually is not the case for a departed user whose account is disabled. It also captures a point-in-time copy with no report of what was included.

Why You Are Probably Doing This: The Departed-User Problem

Be honest about the trigger. Almost every "export mailbox to PST" project is really this scenario: someone has left the company, their mailbox must be kept - for legal, compliance, or continuity reasons - and you want their Microsoft 365 licence back. The licence maths drives it: a Microsoft 365 E3 licence lists at roughly US$36 per user per month, so every departed user whose licence is kept alive just to preserve a mailbox costs around US$430 a year. Twenty departures a year handled that way is a five-figure annual bill for data nobody is using.

PST export looks like the free answer. It is worth knowing what you are actually getting.

Why a PST Is Not an Archive

A PST is a transport format, not a retention strategy. The problems compound over time:

• Fragile and corruptible. PSTs are single files that corrupt, and large ones corrupt more often. A damaged PST containing the only copy of a departed executive's mailbox is a bad day years in the making.
• Easy to lose, hard to secure. Once exported, the PST lives on a file share, a desktop, or a USB drive - outside your identity controls, outside your DLP, invisible to audit. Anyone with the file has the mailbox.
• Not searchable at scale. Legal asks "what did these five former employees say about project X?" With PSTs, someone mounts each file in Outlook and searches by hand.
• No retention enforcement, no immutability. Nothing stops a PST being edited, partially deleted, or quietly discarded. For legal hold purposes, a loose file is a weak answer.
• It does not scale. The Purview export flow above is fine once. Run it for every leaver - search, export, wait, download, verify, file away, document - and it becomes a recurring manual job that someone forgets during a busy month.
• It does not touch OneDrive. The departed user's files are a separate problem PST export does nothing about.

The Other Workaround: Converting to a Shared Mailbox

The common alternative is converting the departed user's mailbox to a shared mailbox, which frees the licence and keeps the mail visible. It has its own trap: unlicensed shared mailboxes are capped at 50 GB, long-tenured leavers often exceed that (which puts you straight back into licensing), there is no litigation hold or retention coverage without a licence, and OneDrive is again ignored. The full breakdown is in how to archive a shared mailbox - including why five years of this pattern leaves a tenant full of orphan mailboxes nobody dares delete.

The Automated Alternative: Chipmunk

Chipmunk exists for exactly this scenario. Instead of a manual export per leaver, it detects disabled accounts in Microsoft Entra ID and automatically archives the departed user's Exchange Online mailbox and OneDrive into Azure Blob Storage in your own subscription. Then the licence goes back into the pool.

What that changes compared to a folder of PSTs:

• The data stays searchable - archived content is indexed and retrievable without mounting files in Outlook.
• Retention is enforceable. The archive sits in your Azure storage, where you can apply retention settings and immutable (WORM) tiers for compliance-grade preservation.
• Every action is audited. A full audit trail records what was archived and when, and what was restored.
• You own the storage. The archive is in your Azure subscription, in your chosen region - not in a vendor's cloud, not in a loose file. If you ever stop using Chipmunk, the data is still yours, readable with standard Azure tools.
• It scales. One leaver or two hundred - the workflow is the same, and nobody has to remember to run it.

Chipmunk deploys from the Azure Marketplace into your own environment. The full workflow is covered in the Microsoft 365 departed user archiving guide.

PST Export vs Shared Mailbox vs Chipmunk

	PST export	Shared-mailbox conversion	Chipmunk
Reliability	Single file, corruption-prone	Fine until the 50 GB cap	Archived to Azure Blob Storage with platform durability
Searchable	Only by mounting in Outlook	Yes, while it exists	Yes - indexed and searchable
Retention / immutability	None	None without a licence	Retention settings and immutable tiers in your Azure
Audit trail	None	Standard mailbox auditing	Full archive and restore audit trail
OneDrive included	No	No	Yes
Licence reclaimed	Yes	Yes (until it exceeds 50 GB)	Yes
Scales to many leavers	Manual per mailbox	Accumulates orphan mailboxes	Automated on account disable

Frequently Asked Questions

How do I export an Office 365 mailbox to PST? Use eDiscovery in the Microsoft Purview portal: create a case, create a search scoped to the mailbox, select Export with "Create PSTs for messages", and download the package from Process manager in your browser. The classic Content Search interface, the ClickOnce export tool, and the PowerShell New-ComplianceSearchAction -Export command were all retired by Microsoft in 2025, so guides describing those methods are out of date.

Is PST a good archive format? No. PST is a useful transport format but a poor archive: files corrupt, sit outside your security and audit controls once exported, cannot be searched at scale, and carry no retention enforcement or immutability. For a one-off export it is fine; as the long-term home of departed employees' data it is a liability that grows with every leaver.

How do I keep a departed user's email without paying for their licence? The two manual workarounds are PST export (fragile, unsearchable, no OneDrive) and shared-mailbox conversion (50 GB cap, no hold coverage, no OneDrive). The automated pattern is Chipmunk: it archives the departed user's mailbox and OneDrive into your own Azure storage - searchable, auditable, with retention and immutable tiers available - and the licence is reclaimed. It deploys from the Azure Marketplace into your own environment.

Related reading

• How to export a Teams chat - the same departed-user problem, for chat instead of mail.
• Microsoft 365 departed user archiving: the full workflow
• How to archive a shared mailbox
• Stop paying for Microsoft 365 licences after staff leave
• Inactive vs shared vs archive mailbox

Stop Exporting Mailboxes by Hand

If PST exports have become a recurring offboarding chore, see how Chipmunk automates departed-user archiving - it deploys from the Azure Marketplace into your own Azure environment. Questions: sales@smikar.com.