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3 Easy Ways To Compact OST File

Sometimes you may see that people are working on their Outlook mailbox even when there is no connectivity with the Internet. This can bring a question in your mind that how is it possible to work with an email client when there is no internet connectivity. Well, this all is possible because of the Outlook’s feature to work in offline mode. This feature of Outlook facilitates you to create and modify emails, edit contacts, and do many such Outlook operations even when there is no connection to the network is available.

Whenever an Outlook user initiates his/her working in Offline mode, the Offline Storage Table (.OST) file is created. This .OST file is saved on local hard drive of user’s computer. However, all the changes that a user has made during offline mode are synced with his/her mailbox on Exchange Server only when he/she gets connected with the network. However, an Outlook user may feel performance issues when the OST file gets large in size, such as 2GB for Outlook 2003 and earlier Outlook versions.

 Moreover, large size of Outlook OST files not only deteriorates the performance of Outlook, but can corrupt the OST file, and thus can create inaccessibility of your Outlook data. Therefore, it is recommended to compact the size of your OST file in a way that neither data get lost, nor Outlook working stops. Outlook gives you option to compact your Outlook data files. Mentioned below are steps to compact your OST file:

 Method 1: Steps to compact OST in Outlook 2003 and earlier Outlook versions:

  • Go to ‘Tools’ menu and click ‘Email Accounts’.

  • Select ‘View or change existing email account’, and then click ‘Next.

  • Select ‘More Settings’.

  • On the ‘Advanced’ tab, click ‘Offline Folder File Settings’.

  • And then click ‘Compact Now’.

Method 2: Steps to compact OST in Outlook 2007:

  • Go to the ‘Tools’ menu and then select ‘Account Settings’.

  • Here in the list, select ‘Microsoft Exchange Server’, and then click ‘Change’.

  • Go to ‘More Settings’.

  • Click ‘Advanced’ tab, click ‘Offline Folder File Settings’.

  • And then click ‘Compact Now’.

Method 3: Steps to compact OST in Outlook 2010:

  • On the ribbon, click ‘File’ tab and then ‘Info’ tab on the menu.

  • Click ‘Accounts Settings’ provided under ‘Accounts Settings’ tab.

  • Select ‘Microsoft Exchange Server’ from this list, and then click ‘Change’.

  • Click on ‘More Settings’.

  • Then on the ‘Advanced’ tab, click ‘Offline Folder Settings’.

  • And then click ‘Compact Now’.

However, before performing OST compaction, your .OST file must meet the below listed requirements:

  • The .OST file must be of 16 KB or larger.

  • The .OST file must have free space of minimum 16KB since the last time you have compacted it.

The compaction of OST file in Outlook 2010 depends upon the items that you have marked for deletion, which can make compaction process useless. Therefore, it is recommended to keep the backup of current OST files and delete useless and large emails from your Outlook mailbox. This will reduce your OST’s size and make compaction easier.

Written By

I am Data Recovery Expert from Stellar Information System Ltd and currently doing research on Outlook PST Recovery Software, Outlook Express Recovery, Exchange Recovery.



  1. john_oliver01

    July 3, 2013 at 10:17 am

    Thanks for sharing this helpful resource there are also some third party applications which help to compact & repair corrupt OST file. Also try Kernel for OST to PST converter tool to repair the corrupt OST file and converting them MS outlook .PST file.

  2. marry

    December 27, 2013 at 5:15 am

    I have used this software and I found this software really effective and easy to use. This software efficiently repairs damaged PST as well as OST files. This software also generates the preview of all recoverable files

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