Export Outlook emails for records and cases

MSG or EML?

When in doubt, export both: they come from the same source and serve different readers.

For a few messages: drag them out of Outlook

In classic Outlook for Windows, drag a message from the list into a folder in File Explorer. Outlook saves it as an .msg file. For a handful of messages this is the quickest way.

It does not scale: hundreds of messages, nested folders and consistent file names are slow and error-prone by hand.

For a whole mailbox or folder: export the PST

1. Get the mail into a PST. In classic Outlook use File › Open & Export › Import/Export › Export to a file › Outlook Data File (.pst), select the folders and save. If you only have the .ost of a former account, convert it with OST to PST.
2. Record the original. Before anything else, note the PST’s size and a checksum, so you can show later that it was not changed. On Windows, in Command Prompt:

   certutil -hashfile "C:\path\to\mailbox.pst" SHA256

   On a Mac, in Terminal: shasum -a 256 /path/to/mailbox.pst.
3. Export. Open PST to MSG or PST to EML, choose the PST, run the free check, then convert. You get one ZIP with a file per message, arranged in the mailbox’s folder structure.
4. Check the counts. The report shows how many messages were exported and lists anything that could not be. Every file is read back and compared with the PST before the ZIP is offered.
5. Hash again. Run the same checksum command on the PST: the value is unchanged. The tools never write to your source file.

The export runs in your browser, on your computer. Nothing is uploaded, which matters for confidential mail.

Keep the set usable

• Keep the PST, the ZIP and the report together, with the checksum you recorded.
• Do not open and re-save individual .msg files in Outlook if they are evidence: opening is fine, saving changes can alter properties.
• Need to search the set first? Open the PST in the PST Viewer and search by sender or subject before deciding what to export.

Formal legal holds

For mailboxes still on Microsoft 365 or Exchange, formal eDiscovery (search, hold and export with an audit trail) is done by your organisation’s administrators with Microsoft Purview. File exports like these suit records, small matters, personal archives and mail that exists only in PST or OST files. If a court or regulator sets a specific format, follow their requirements.

Frequently asked

Are attachments kept? Yes. In MSG files every attachment and attached Outlook item stays inside the message; in EML files ordinary attachments are standard MIME parts of the message. Attached Outlook items (a message forwarded as an attachment) are kept in MSG; in EML they are listed in the report but not converted yet.

Can I go back from files to a PST? Yes: MSG to PST and EML to PST collect the files into a new PST, keeping folders.

What is not exported? Contacts, calendar items and tasks become messages in EML; MSG keeps their fields. The report lists anything left out.