To access emails stored in a PST file on a Mac without changing the original data, the safest approach is to use a PST viewer that lets you open and read mailbox contents without importing the file into Outlook. You can also keep a separate backup of the PST file before opening it for additional peace of mind.
You can use MacSonik PST Viewer for Mac to open PST files on macOS without installing Microsoft Outlook. It lets you preview emails, attachments, contacts, calendars, and other mailbox items while maintaining the original folder structure. The software processes files locally on your Mac rather than uploading them to external servers.

How to access PST emails safely:
1. Download and install MacSonik PST Viewer.
2. Launch the software and select the option to add a PST file.
3. Browse your Mac and choose the PST file you want to view.
4. Expand the mailbox folders to access Inbox, Sent Items, and archived emails.
5. Select an email to read its contents, inspect its headers, or view its attachments.
If your priority is protecting the original data, keep an untouched backup of the PST file and avoid saving changes to the source file. You can also preview emails before exporting selected items into formats such as PDF, EML, or MSG.