How to View OST File in Outlook 2019, 2016, 2013? Reliable Solution

If the Outlook OST file exceeds its prescribed size limit, it is easily damaged. In this case, it will be difficult to view the OST file in Outlook. So how can users extract or view valuable data stored in inaccessible OST files through Outlook 2016, 2019?

When Outlook is used with “Cached Mode”, all data stored in the Microsoft Exchange email account on the local system will be saved for offline access. This offline copy of Exchange account data is called an offline storage table file or OST file. OST files allow users to operate their mailboxes in offline mode, even if the connection to Exchange Server is temporarily unavailable. After the connection is restored, all changes made to the mailbox will be synchronized with the online account.

While Outlook is an efficient email client, Outlook often has problems due to OST file issues. One of the main problems with OST files is that they can become corrupted if the file size exceeds a certain limit. File corruption can make it impossible to access the data stored in such OST files. Therefore, users need to design strategies to overcome this problem and access their valuable mailbox data.

Reasons for Outlook OST File Reaching a Maximum Size

Why has the OST file become too large and how to resolve it immediately? Let’s know:

  • The Outlook versions that came before Outlook 2002 used a data file format called ANSI. This came with a file size limitation of 2GB. This limit was exhausted in a few months’ time, especially with large attachments.
  • The later versions of the application used UNICODE data files, which had a file size limitation of 20 GB. But the same problem recurred due to regular usage, leading to size issues.
  • Having two versions of Outlook installed on the same device can hamper Outlook updates, ultimately leading to oversized files.

The direct way to resolve a very large OST is to delete unnecessary emails, as the more email exchanges occur, the more space it will take up. However, because many conversations are important, this may not really be possible for all users. Furthermore, in most cases, even if some emails are deleted, the error still exists. Therefore, to view an OST file in Outlook that exceeded its size limit, some other solutions are required.

How to View OST File without Outlook With Reliable Solution

The offline Outlook folders allow users to operate even without an Internet connection. There are synchronization issues, incorrect network connection, faulty device configuration, etc. Some of the main factors that cause the OST file to be orphaned or damaged. To make the OST file accessible again, please use the FreeViewer OST File Reader Tool. It is completely free software, you can view or even view OST files without installing the Outlook application on Windows OS. The tool also counts the counting of items for each folder and subfolder. Additionally, it can unlock the OST without an Exchange Server environment.

Steps to View OST File without Outlook on Windows OS:

  • Run Free OST Viewer Tool and Click “Add File” to Load OST File Data

Add OST File

  • View Contents of Outlook OST File in Preview Panel

View OST File without Outlook

  • Change the Screen Viewing Mode, Namely Horizontal and Vertical

Screen View Options

  • View OST Mailbox Items, that is, Calendar, Contacts, Tasks, Notes, etc.

View Mailbox Items


While OST files are very useful, their management can easily get out of control if you don’t pay attention to them in time. While using the manual method to view OST file in Outlook PST format is the best solution to this problem, if the manual method does not work, you can always rely on the automatic and efficient solution to solve this problem.