How to open an OST File in Office 365?

An OST file (Offline Storage Table) is a local copy of your mailbox stored on your computer. It allows you to access your email, calendar, and contacts offline and make changes that will sync with the Exchange server the next time you connect. If you are using Office 365, you can open an OST file by following these steps:

1. Access Outlook and navigate the "File" tab in the top left corner.
2. From the "Account Information" section, click on the "Account Settings" button.
3. From the "Account Settings" window, select the "Data Files" tab.
4. Click the "Add" button to open the "Open Outlook Data File" window.
5. Please navigate to the location of the OST file on your computer and select it.
6. Click "Open" to add the OST file to Outlook.

Note: If the OST file is password-protected, you must enter the password before it opens.

Once you import the OST file to Outlook, you can access the email, calendar, and contacts stored in it, just like any other email account. You can also go for any third-party OST to Office 365 Migration software.

Keep in mind that any changes you make to the OST file will be synced with the Exchange server once you are connected to the Internet, and Outlook can sync with the server.