Recover the emails from an .ost file, even without the original account
Closed Exchange account, dead server: the .ost file is often the only remaining copy of your messages. This tool reads it directly and recreates emails and folders in the mailbox of your choice.
OST vs PST: what’s the difference?
The .ost file is the offline cache Outlook maintains for an Exchange or Microsoft 365 account: a local, continuously synchronised copy of the mailbox. The .pst is a deliberate export archive. While the original account still exists, the cleanest path is exporting a .pst from Outlook. But once the account is gone — company offboarding, cancelled subscription, dead server — the OST is often the only remaining copy of the messages, and Outlook refuses to open it without the account. This tool reads the .ost file directly and sends its contents into the IMAP mailbox of your choice.
How it works
- Locate the .ost file — on Windows, usually in
C:\Users\<you>\AppData\Local\Microsoft\Outlook. - Upload it here — up to 5 GB in total; .pst files are accepted too.
- Enter the destination mailbox — credentials and IMAP server.
- Launch — messages and the folder tree are recreated in the mailbox, with their original dates.
What the tool doesn’t do / limits
- Only emails are imported — contacts, calendars and tasks are skipped and counted in the report.
- An OST reflects the state of the last synchronisation: anything not synced before the cutoff isn’t in it.
- If the original account is still active, prefer a .pst export from Outlook, then the PST to mailbox tool: an export is more complete than a cache.
- The free limit is 5 GB of archives per import; beyond that, one-off pricing or Premium.
Frequently asked questions
Outlook refuses to open my .ost — will this tool manage? +
Yes, that is exactly its purpose. Outlook only opens an .ost when it is linked to the original Exchange account; this tool reads the file itself, no account needed, and extracts the messages. If the file is encrypted or corrupted beyond reading, the import fails with a clear message — nothing is written to your mailbox in that case.
Will I get ALL my messages back? +
Everything the file contains: an .ost reflects the last synchronisation with the server. Anything not synced before the cutoff isn't in it. Contacts, calendars and tasks are not imported (their count is shown in the report).
My account still works — what should I do? +
Export a .pst from Outlook instead (File → Open & Export → Import/Export): a deliberate export is more complete than a cache. Then import it with the PST to mailbox tool — the form here is the same, both formats are accepted.
How much does it cost? +
Free up to 5 GB of archives per import. Beyond that, €5.99 incl. VAT one-off, or unlimited volume with Premium. The threshold is the same for everyone.