How to Open an OST File in Outlook: Complete Guide for 2019, 2021, 2024, and Microsoft 365

OST file is created when you set up an Exchange, IMAP, Microsoft 365, or Outlook.com account in Outlook. It is an offline, cached copy of your mailbox data on the server. This data file is linked to the particular profile in which it is created and is encrypted with the unique MAPIEntryID GUID key. If your Outlook profile is deleted or the mailbox is disabled from the server, the associated OST file becomes orphaned or inaccessible. Thus, it can’t be opened, imported, or accessed directly in any other Outlook profile or account.

However, you can still recover and open your mailbox items by converting the OST file into PST, which you can open in any Outlook profile. In this blog, we will be discussing how to open OST file in Outlook 2024, 2021, 2019, 2016, 2013, 2010, and 2007.

Why you Need to Open OST File in Outlook?

You need to open an OST file in another Outlook profile in the following situations:

• The original profile has been deleted or damaged.
• The associated Exchange or Microsoft 365 account is no longer available.
• You are trying to access the file in a different account or profile.
• The OST file has become inaccessible or orphaned.
• You want to access an old OST without connecting to the original mailbox.

Methods to Open OST Files in Outlook

You can follow the below methods to open OST file in Outlook.

Method 1: Reconnect the Original Account

If the original Exchange, Microsoft 365, or Outlook.com account is still active, you can add or reconnect it to Outlook. The email client will recreate the OST file and synchronize the mailbox data from the server. Here are the steps to reconnect the original account:

• Go to the File menu in Outlook and click on Add Account.

• On the window that opens, enter the credentials of the original email account. Follow the prompts to complete the setup.
• Restart Outlook. It will create a new OST file and synchronize all your mailbox data available on the server.

This method will work if your account associated with the OST file is available on the server. If not, then follow the next method.

Method 2: Convert the OST File to PST

If the account is unavailable on the server or the OST has become orphaned, you need to convert your OST file to PST format by using an OST to PST converter. For this, you can use Stellar Converter for OST. It can convert inaccessible, orphaned, or encrypted OST file into PST format by maintaining original folder structure and hierarchy. It also provides option to save the mail items in RTF, MSG, PDF, EML, and HTML formats. The software can open OST files without Exchange Server and save all mailbox items, such as emails, contacts, calendars, notes, attachments, etc. to PST format with complete data integrity.

There are two editions of the software: Corporate and Technician. The Technician version also lets you export the converted OST mailbox items directly to an existing Outlook profile on your system, Office 365 account, or live Exchange Server.

After converting the OST to PST, you can open or import the file into any Outlook version and access the mail items.

To know how to convert OST to PST by using Stellar Converter for OST, watch this video:

Conclusion

You cannot directly open or import an OST file in any Outlook account. You need to first convert it into PST format. If your OST file is active, you can use the Import and Export feature to convert it to PST file and then import this file into Outlook. If your OST file is inaccessible or orphaned, you need to use a specialized OST to PST converter software, such as Stellar Converter for OST. By using this software, you can convert and also export the OST mailbox items to other formats, such as RTF, MSG, PDF, and EML, or export OST items directly to your Office 365 account, existing Outlook profile, or live Exchange Server.

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