For a deleted PST, recover the archive file first and then inspect its items in Outlook. A PST archive, an OST cache and a server mailbox are different recovery sources. Rebuilding an Exchange OST from the server is not a way to restore an independently deleted PST archive.
Identify the missing data store
This workflow uses classic Outlook for Windows. Under File > Account Settings > Account Settings > Data Files, inspect the path of listed data files. A typical newer PST location is Documents\Outlook Files, but archives may have been stored elsewhere. Use the actual path and account, rather than scanning a default folder by assumption.
If messages are missing only from a server mailbox, inspect the mailbox’s Deleted Items/recoverable-items facilities and organizational retention. If the missing content existed only in a local PST, server-side recovery may not contain it. If an OST may contain unsynchronized work, preserve it before considering cache recreation.
Find the deleted PST
Close Outlook before copying a PST that is still in use. Check Recycle Bin, the original archive folder, existing backups and any explicit PST export. If the PST was on an external disk, inspect that disk rather than only Windows’ system drive.
If no copy exists and the storage is readable, XRecovery can search for remaining files. Browse the former directory and search by filename or .pst where available. Save candidates to another physical device. General file recovery does not guarantee item-level completeness in a recovered mail store.
Open a working copy in classic Outlook
Keep the recovered original untouched. In classic Outlook choose File > Open & Export > Open Outlook Data File, select the working PST copy and expand its folder tree. Change search scope to include the archive when looking for messages. Microsoft documents this in Open and find items in a PST.
Do not import everything into a live mailbox as the first verification step. Opening the separate copy lets you inspect its contents without merging incomplete or duplicate items into the production store. New Outlook has different PST support and entry points; the classic steps above are not interchangeable with it.
Handle errors without losing the candidate
For an existing PST that reports errors, Microsoft’s SCANPST.EXE is a native diagnostic/repair route. Exit Outlook, retain an independent copy, select the working PST in SCANPST, scan and review findings before repair. Microsoft notes that some items may remain unrecoverable. See Repair Outlook data files.
Keep disk-file recovery separate from the Outlook repair workflow. Use Outlook’s documented repair route on a copy when the recovered PST needs structural checking.
Verify several known messages across folders and dates, attachments, contacts and calendar items relevant to the archive. Compare expected counts where reliable, but also open actual items. An empty folder tree or searchable subject alone is not proof that message bodies and attachments survived.
For the next step, see Document Recovery: Deleted, Unsaved, Overwritten or Damaged?.