OST file format from ol 2013 RRS feed

  • Question

  • Could someone say what exactly changed to OST file format since Outlook 2013 ?

    I have read that:
    By default, when Outlook 2013 is installed, a new compressed version of the Outlook data file (.ost) is created. This new compressed version of the .ost is up to 40% smaller than the .ost files that were created by earlier versions of Outlook.

    But what exactly changed in this new compressed version? We have an important product that works with not connected OST files and we are using PST.NET (by independentsoft) component which provide the functionality for getting info from not connected OST files. However OST files that are created by Outlook 2013 can't be opened because the structure is different from OST files created by older Outlook.

    Tuesday, January 29, 2013 8:35 AM


All replies

  • I think ost format is undocumented - you will have to wait for your software provider to provide new version that handles these changes.
    Tuesday, January 29, 2013 8:48 AM
  • Hi,

    Yes, few things has changed, some structures are different and compression was added. As far as I know there is no documentation regarding that changed so I had to do it the "hard way". 

    If you are interested in the solution, let me know. 

    Best Regards,


    Wednesday, September 10, 2014 1:53 PM
  • Hi,
    Thank you for coming up with a solution. Could you tell me more about it ?

    Wednesday, September 10, 2014 1:57 PM
  • Hi, 

    I am (was) in the same situation. I discovered that OST 2013 is not supported by Independentsoft .NET PST library. I requested support from Independentsoft as I have bought their source codes in the past. They know about the issue but they are not planning to implement it soon. The OST 2013 has a lot of differences.  As I use to do this “kind of things” for living so I decided to do it myself. I have figured out all the differences (including compression) and implemented in their source code. Until now I have successfully tested it on over 1 million emails extracted from OST 2013. The changes I've made in their source code does not affect previous versions.  I might offer them to buy it from me, so maybe soon they will be supporting OST 2013.

    Best Regards,


    • Edited by Matt Janda Thursday, September 11, 2014 10:28 AM
    Thursday, September 11, 2014 10:25 AM
  • Do you have Independentsoft .NET PST source codes ? If you have bought the source codes, then adding about 5000 lines of my code could solve the problem. 

    • Edited by Matt Janda Thursday, September 11, 2014 11:02 AM
    Thursday, September 11, 2014 10:29 AM
  • Hi,

    At some point I will be releasing document with all differences in OST2013.

    The document will cover only the differences so I assume you have got already previous OST/PST versions covered.  

    If you are trying to solve it on your own I can give you few hints...


    The major changes were made in followings: 

    Heap-on-Node (HID)
    B-Tree page (BTPAGE)
    Leaf BBT Entry (BBTENTRY)
    Data Blocks (compression)

    Best Regards,

    Matthew(.janda at hotmail dot com)

    If you are interested in ready solution the way would be to buy Independentsoft .NET PST library and I can provide upgrade for their source code. 

    • Edited by Matt Janda Friday, September 19, 2014 7:22 AM
    Friday, September 12, 2014 9:54 AM
  • Hi Matt, I emailed you about your solution. We bought and have been using IndependentSoft PST.NET library for a while. How can we get your changes that support OST 2013?


    msaleh6 at hotmail dot com

    Wednesday, February 3, 2016 1:19 PM