Easy Ways to Convert OST to PST File Format in Various Situations

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The authenticity of Exchange environment is also maintained in its offline data storage file. This is the reason why OST file refuses to open in various conditions where MS Exchange account is unavailable. However, for each such case and other cases there are different ways to convert OST to PST file.  Here we will be discussing various scenarios and respective methods for the conversion of OST to PST file. First we will see what bounds OST file accessibility;

Why OST Cannot be Accessed?

OST file is bound to a particular MAPI profile. Its access can be only done when you log in and authenticate using the profile originally used to create an OST file. In case you don’t do this, client will deny opening Exchange OST file. The reason behind this is that the specific user account for which the OST is configured stores an encrypted cookie in the registry. This encrypted cookie is generated from mailbox’s unique ID. The mailbox unique ID can only be accessed when connected to server, so it follows that an initial connection must be made to create the cookie and store it into the MAPI profile. Whenever you connect through offline mode, the profile is read to check whether the cookie exists or not. In case profile is unavailable, OST will refuse to load issuing a warning that connection to server must be made to recreate the cookie.

Let us now see, various scenarios under and allied methods to perform OST to PST conversion;

Various Methods for OST to PST Conversion

Case 1: MS Exchange Account Is Active

Conversion of OST data to PST cannot be done directly. As mentioned above, OST is tied to the MAPI profile for which it has been created and in order to follow this procedure, MAPI profile must be active and you need to log in with original MAPI profile simultaneously. Once it is done you can copy or export the OST data to PST file. Follow the below mentioned steps;

  • Open MS Outlook application
  • Go to Import & Export option
  • Choose Export to a File
  • Personal Folder File (.pst)
  • Select the Mailbox Folders to be exported to PST
  • Provide location to save PST file
  • Click Finish

Note: This process can only be done when your Exchange Server is up and connectivity of it with MS Outlook is proper.

Case 2: OST is Corrupted But Exchange Account is Available

OST being a copy of Exchange mailbox saved on server is a complete replica of data saved on server. This means even if the OST is corrupted it can be recreated and assembled downloading all the data again in it. As mentioned above OST is stamped with a unique ID so necessary settings have to be done to recreate it. Follow the below mentioned steps to recreate OST;

  • Locate OST file on the disk.
  • Right-click and select Rename.
  • Change extension from .ost to .ost.old and hit Enter.
  • Now access your Exchange Server account and open Outlook.
  • MS Outlook will re-configure the data file.
  • The new OST file will not be corrupted and the data can be accessed without any errors.
  • Now you have a healthy OST file and you can follow the steps mentioned in Case 1 to convert OST data to PST file.

Case 3: OST is Corrupted & Exchange Account is Unavailable

In this case, as the MS Exchange account is unavailable this means that the MAPI profile for which the OST is being created does not exist. The unavailability of Exchange account can be lead due to many reasons like;

  • Exchange account got accidentally deleted.
  • MS Exchange is suffering from downtime.
  • MS Exchange is being upgraded and thus accounts are unavailable for access.
  • Exchange Server got crashed or corrupted.
  • The Exchange database is having issues.

In all above cases MS Exchange account is unavailable and thus neither the inbuilt repair mechanism can work on OST file nor can the above mentioned methods work. In such situation a wise technique to convert OST to PST file is relying on professional software like QuickData OST to PST file. Such software also work for orphan and inaccessible OST file and performs the conversion is very less time maintaining the precision.


OST inaccessibility issues are frantic when it is the only source left to access data from. OST to PST conversion can be a wise tactic but this conversion also depends on the resources and environment available. This article clears the idea of situations where OST can be converted directly and where some extra settings and efforts have to be taken. It also clarifies the reason why OST cannot be accessed and how to make it accessible under various situations.



My name is Zora Stalin, I am a tech guy working on an IT company as a technical assistant manager from past 5 years. Writing tips based blogs, articles and product reviews is my passion.

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