.ost file: how to open it on Windows
2 Windows apps register the .ost extension. Install one of them to open the file with a double-click.
- PST Walker
View all items in OST or PST file, whether they're emails, tasks, contacts, notes, calendar events, or attachments, you can easily open them all.
- Stellar Converter for OST
The tool converts orphaned OST files to PST, including emails, attachments, contacts, and calendars with 100% precision.
Related guide: Change the default app for a file type in Windows