Member Avatar for baldwinW

Hi. Help me to understand. The problem has one of the employees, he demolished mail, while maintaining files .ost. In fact there should be no problems. Always when the client connects to the Outlook (if storage was Mailbox Exchange) is automatically pulled from the mail server. But this is not happening. It draws only the contacts and everything. I looked a mailbox on a server size of 20kb. And the size of the .ost 135mb. It is logical that there is a server-mails therefore they .ost. Surfing network I found pair program conversion .ost to .pst. But they didn’t help. Are there any fast methods to do this?

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Brief recap and where to start: reports an OST much larger than the mailbox on the server and mail visible only in the local file. That pattern usually means the server copy is empty (or was removed) while the workstation kept a cached copy. is right to be suspicious of “one‑click” converters, and is correct that the OST is a cache rather than the authoritative mailbox. Two safe recovery paths are available: get the server/mailbox restored by an Exchange admin, or extract the contents from the OST into a PST on the workstation.

Practical recovery checklist:

  • Verify the server state first using Outlook Web Access (OWA) or the Exchange Admin Center to confirm whether mail really is gone from the server.
  • If the Exchange account still exists and Outlook opens the mailbox: create a new Outlook Data File (PST) and use File > Open & Export > Import/Export > Export to a file > Outlook Data File (.pst) to export the mailbox (include subfolders).
  • If the account was removed and the OST is the only copy, copy the OST file to a safe location first (do not work on the original). Then either (a) ask Exchange admins to restore the mailbox from backup or the Recoverable Items folder, or (b) use an expert offline extraction method to move data into a PST.

Advanced extraction (expert-level, non‑destructive approach):

  • Create an empty PST in Outlook (Account Settings > Data Files > Add).
  • Use a trusted low‑level MAPI tool (for example, MFCMAPI) to open the profile that points to the OST and the newly created PST store, then copy folders/messages from the OST store into the PST. This is an advanced operation; make a full file backup first and work on copies only.

Notes and cautions: never run untrusted “OST-to-PST” executables on the only copy; that risks corruption. Always work from a copy of the OST, and escalate to the Exchange administrator or a competent IT pro if server restores are possible. The safest route is restoring the server mailbox (if backups exist) or exporting via Outlook when the account can be reconnected.

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Member Avatar for rproffitt

I see you asked at and there's a fine answer there.

What does not work are those repair tools you see spammed a lot. Don't fall for that spam!

Member Avatar for david parrish

It sounds like the user created a PST to store their files, instead of deleting them, correct?
The user can open Outlook but they do not receive any new email. They just see contacts, etc.
Their mailbox on the exchange server is 20kb.
The size of their OST doesn't matter. That's just Outlook's storage file on the workstation. That's where email is saved to on the workstation.
Is the user receiving new emails? Can you check the Exchange routing log to check if email is delivered to the user?
It sounds like when creating the PST file, the user deleted their Exchange account from Outlook.

Edited by happygeek because: spam removed
commented: To restore data from OST files into outlook data file format, OST to PST conversion tool is the most appropriate tool. It allows to convert multiple O +0
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