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How to Fix Oversized OST File Issue in Outlook?

Email | 6 min read| Brayden Mitchell | Updated On - November 19, 2022

Are you aware of the 2GB truncation resolution in Outlook OST Files?

Got a new mail in your Outlook mailbox? The happiest moment indeed. But it may not keep you happy any longer as your mailbox is soon going to exceed it saving capacity. Whenever such situation happens there are chances that the stack of OST files may get corrupt leading to affect the linkage between Exchange Servers and Outlook.

What is the whole Story?

Every Outlook version has its limitation of saving the OST files which are the copy of PST files maintained in the user’s system. This copy is shared to the other client by exchange servers that act as the post office virtually. To save the Outlook OST files in the system, the Outlook versions provide certain limitations beyond which storing the OST files is not recommended. The 2GB truncation error is one of them.

MS Outlook 2002 and prior versions provide limitation to the user to save not more than 2GB of OST files in the mailbox. Even though when the user deletes them, the files go to the bin; however, space occupied by the files in the hard disk remain unchanged. When user ignores the warning, the heap of OST files keep on accumulating and finally leads to corruption in the form of inaccessibility. To avoid such incident to happen and making clean swipe of the unused OST files, it is advised to go for hard deletion i.e. shift + delete.

How to recognize 2GB OST error?

The 2GB OST error manifests due to over sizing of OST files. Once the OST files are oversized, the Outlook generates following messages:

  1. Errors have been detected in the file xxxx.ost. Quit all mail-enabled applications, and then use the Inbox Repair Tool.
  2. Task ‘Microsoft Exchange Server’ reported error (0x00040820):’Errors in background synchronisation. In most cases, further information is available in a synchronisation log in the Deleted Items folder.’
  3. Can’t copy the item.

If any of the above mentioned OST error flashes on the screen, then it is confirmed that Outlook mailbox space is saturated and needs selective deletion of the OST files which are trash.

However, for all Outlook versions some common issues faced by the oversized OST file are:

  • Corruptions in OST file
  • Unable to edit or modify OST file content
  • Different error messages while synchronizing data
  • Freezing, slow performance, etc. Issues while using the application
  • Cannot access or download Outlook emails

Resolutions to fix Oversized OST files

The maximum OST file size for Outlook 2010 and above version is 50GB beyond which the problems occur. The oversized OST files can be fixed either by deleting the unnecessary OST files or by compressing the OST file volume or by taking assistance from the third-party.

  • Hard deletion of OST files: The deletion of files using shift+delete that permanently deletes the files even from the hard disk is called hard deletion. The process of hard deletion is exercised when the OST files are to be deleted permanently. This empties some space in the hard disk so that the new OST files can be saved. A new updated OST file will be automatically generated once the Outlook application is restarted and the Exchange Server is configured again.
  • Compression of OST files: To compress the OST files and to add some space to the hard disk user has to follow the following steps:
  1. Click Menu->Go to Folder List-> Click Inbox.
  2. Click Properties->Clear Offline Items.
  3. Click Tools -> Account Settings.
    Click Tools -> Account Settings
  4. Click Data Files tab -> Select Exchange account’s OST data file. A Microsoft Exchange Screen will appear.
    Select Exchange account’s OST data file
  5. Click Advanced tab followed by Offline Folder File Settings, then
    Click Advanced tab followed by Offline Folder File Settings
  6. Click ‘Compact Now’.

These compaction instructions are for Oversized ANSI OST files. Before implying on these instructions it is requested to check the OST file format.

  • Disable Outlook Add-Ins: Add-ins to Outlook may cause performance issue in oversized OST file. So, it is suggested to disable the Outlook Add-ins. Go to File>Options in the Outlook application. Click on Go against Manage COM Add-ins section and unselect the Add-ins and click on the Disable option to disable it.
  • Archiving OST data files to PST: The Archiving feature in the Outlook application would archive the old offline OST file emails to Outlook PST file format and secure some space on the storage file. Just go to File>Cleanup Tools>Mailbox Cleanup, select the Archive option to archive the OST file or choose another option to delete deleted items from the OST mailbox Deleted Items Folder.
  • Managing UNICODE Registry Values: This method is opted to increase the OST file size limit depending upon the Outlook version. To change the values in the UNICODE registry, the following steps must be followed:
  1. Click on Start button and type Regedit in the Run window.
  2. Navigate for registry keys:
    HKEY_CURRENT_USER\Software\Policies\Microsoft\Policies\12.0\Outlook\PST for Outlook 2007.
    HKEY_CURRENT_USER\Software\Policies\Microsoft\Policies\14.0\Outlook\PST for Outlook 2010.
    HKEY_CURRENT_USER\Software\Policies\Microsoft\Policies\15.0\Outlook\PST for Outlook 2013.
  3. Right click on MaxLargeFileSize -> Modify -> Type the value in MB in the Value Box.
  4. Right click on WarnLargeFileSize -> Modify ->Type the value in MB in the Value Box.
  5. Exit the Windows Registry Editor.

Once the OST file size limits have been exceeded using the registry values, the OST files can be saved without getting corrupt.

The perfect solution for 2GB OST file error without going into the technical details like other methods is taking assistance from the third-party tool like OST to PST Tool. This tool is very much different from the Microsoft’s Scanost.exe inbuilt solution which does not ensure the complete repair and not suited for large-sized OST file. The professional OST Repair Tool makes space for your OST files without compromising on the performance and properties of the OST file. So, it is always better to take professional assistance rather involving yourself in technical cobwebs.

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