Aspose.Email  for .NET

OST File Viewer for .NET

View OST without needing Microsoft Outlook or Thunderbird installed.

How to View OST File Using C#

In order to view OST file, we’ll use

Aspose.Email for .NET

API which is a feature-rich, powerful and easy to use API for C# platform to be used with any Viewer. Open


package manager, search for Aspose.Email and install. You may also use the following command from the Package Manager Console.

<h3>Package Manager Console Command</h3>

PM> Install-Package Aspose.Email

Steps to View OST via C#

Aspose.Email makes it easy for the developers to view the OST file with just few lines of code.

  1. Load OST file in an instance of MailMessage via Load method
  2. Call the MailMessage.Save method to save OST in HTML format
  3. Call Process.Start with path to resultant HTML to load OST content in default browser

System Requirements

Aspose.Email for .NET is supported on all major operating systems. Just make sure that you have the following prerequisites.

  • Microsoft Windows or a compatible OS with .NET Framework, .NET Core, and Xamarin Platforms
  • Development environment like Microsoft Visual Studio
  • Aspose.Email for .NET referenced in your project

C# code to view OST

string output = System.IO.Path.GetTempPath() + Guid.NewGuid().ToString() + ".html";

// load the OST file in an instance of MailMessage
using (var message = Aspose.Email.MailMessage.Load("template.ost"))
    // save OST in HTML format
    message.Save(output, Aspose.Email.SaveOptions.DefaultHtml);
// load resultant HTML in default browser
  • About Aspose.Email for .NET API

    Aspose.Email is a Microsoft Outlook and Thunderbird formats parsing solution. One can easily create, manipulate, convert email and storage formats such as MSG, EMLX, EML and MHT. Handling of email attachments, customization of message headers and implementation of different network protocols like POP3, IMAP & SMTP to send & receive emails is much easier. Its a standalone API and does not require Microsoft Outlook or any other software installation.

    Free App to View OST

    OST What is OST File Format

    OST or Offline Storage Files represent user's mailbox data in offline mode on local machine upon registration with Exchange Server using Microsoft Outlook. It is automatically created on the first use of Microsoft Outlook upon connectivity with server. Once the file is created, the data is synchronized with the email server so that it is available offline as well in case of disconnectivity from email server. OST files can user mailbox items such as emails, contacts, calendar information, notes, tasks and other similar data. Users can create emails and other data items in OST file even in the absence of connection to the server, but these will not be synchronized with the server. Once the connection is established, the local file is synchronized with the server again so that both the server and the local copy are at the same level of information.

    Read More

    Other Supported Viewer Formats

    Using C#, One can also view many other file formats including.

    EML (Outlook Email Messages)
    EMLX (Apple EMLX Format)
    ICS (iCalendar)
    MBOX (Electronic Mail Messages)
    MSG (Outlook & Exchange Format)
    OFT (Outlook Email Templates)
    PST (Outlook Personal Storage Files)
    VCF (Virtual Card Format)