Yes, it’s possible to change an Outlook OST to PST without losing data, but the method depends on account type and file health.
1.    If the original mailbox is accessible in Outlook (Exchange, Microsoft 365, IMAP):
2.    Open Outlook with the active profile.
3.    Go to File > Open & Export > Import/Export > Export to a file > Outlook Data File (.pst).
4.    Select the mailbox or specific folders, enable “Include subfolders,” and choose a safe location.
5.    Finish to create a PST. This preserves emails, folders, calendar, contacts, and metadata like read status in most cases.
•    If the mailbox/account is not accessible, but Outlook still opens the profile:
•    Create a new PST (Home > New Items > More Items > Outlook Data File).
•    Drag-and-drop folders from the OST mailbox into the PST, or use Copy Folder. This keeps structure and content. For large mailboxes, move in batches.
•    If the OST is orphaned or corrupt:
•    Reconnect to the server so Outlook rebuilds a fresh OST, then export to PST.
•    If reconnection is impossible, consider reputable OST-to-PST utilities that read orphaned OST files in read-only mode to prevent data loss.
Tips to avoid loss: ensure stable Outlook, disable conflicting add-ins, back up the PST after export, and verify item counts/folder sizes before and after conversion.
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