Mailbox RescueOpen an OST file without Outlook
An OST file is Outlook's offline copy of an Exchange, Microsoft 365 or IMAP mailbox. Mailbox Rescue opens OST files directly, without Outlook and without the original account, so you can read the mail and export it to EML or MBOX.
When do you need an OST viewer?
- An old work or school account was closed, but the OST file is still on the PC.
- Outlook was removed or the profile was reset, and the mail only exists in the OST.
- You need to check or keep mail from a former colleague's PC.
Steps
- Find the file: usually
%LOCALAPPDATA%\Microsoft\Outlook\*.ost. Close Outlook, or copy the file somewhere else first. - Open it in Mailbox Rescue and browse the folders.
- Click Export to save the mailbox as EML or MBOX files.
Can I convert OST to PST?
Mailbox Rescue doesn't create PST files yet. It exports OST mailboxes to EML and MBOX, which Thunderbird, Apple Mail and most email programs can import. Single EML messages can also be opened by Outlook.
Windows 10 and 11, Intel/AMD and ARM. No account needed. Works offline.
Frequently asked questions
Do I need Outlook or a Microsoft 365 subscription?
No. Mailbox Rescue reads PST, OST and MSG files directly. Outlook does not need to be installed, and no Microsoft account or subscription is needed.
Is my mailbox uploaded anywhere?
No. Everything happens on your PC. The only thing the app ever sends over the internet is your licence key when you unlock the full version.
What does the free version do?
It opens, searches and shows every message, and saves single attachments, without limits. Bulk export stops after 25 messages so you can check the result before you buy.
Is it a subscription?
No. The full version is $9.99 once and works on up to 3 PCs.
Updated 2026-11-08