Reduce the size of Outlook Data Files (.pst and .ost)

Your Microsoft Outlook mailbox grows as you create and receive items. When you delete items, the size of the Outlook Data File (.pst and .ost) file might not decrease in proportion to the amount of data that you deleted. There are several ways to manage your mailbox and reduce the size of the data file.

The Mailbox Cleanup tool is used to view the size of your mailbox and individual folders. You can also archive older items to an archive Outlook Data File (.pst) and empty your Deleted Items folder.

  1. Click the File tab.

  2. Click Tools > Mailbox Cleanup.

  3. Do any of the following:

    • To view the total size of your mailbox and any individual folders it contains, click View Mailbox Size.

    • To locate older items, select Find items older than n days, enter a number between 1 and 999, and then click Find.

    • To locate large items, select Find items larger than n kilobytes, enter a number between 1 and 9999, and then click Find.

    • To move older items in your mailbox to an archive Outlook Data File (.pst), click AutoArchive.

      Outlook Data Files (.pst) are saved on your computer in the Documents\Outlook Files folder. If you are using Windows XP, .pst files are saved in the My Documents\Outlook Files folder.

    • To view the size of your Deleted Items folder, click View Deleted Items Size.

    • To empty your Deleted Items folder, click Empty.

    • To view the size of your Conflicts folder, click View Conflicts Size.

    • To delete the contents of your Conflicts folder, click Delete.

If you delete items from an Outlook Data File (.pst), the file is automatically compacted in the background when you’re not using your computer and Outlook is running. You can also manually start the compact command immediately. It might take several minutes to compact an Outlook Data File (.pst).

  1. Delete any items that you do not want to keep.

  2. Open the Folder List view. At the bottom of the Navigation Pane, click the Folder List icon or press CTRL+6.

  3. In the Navigation Pane, right-click the Deleted Items folder, and then click Empty Folder.

  4. Click the File tab.

  5. Click Account Settings, and then click Account Settings.

  6. On the Data Files tab, click the data file that you want to compact, and then click Settings.

  7. Click the Advanced tab > Outlook Data File Settings.

  8. In the Outlook Data File Settings dialog, click Compact Now and then click OK.

Note:  You do not have to exit Outlook after you compact an Outlook Data File (.pst) file.

An offline Outlook Data File (.ost) is exclusive to Microsoft Exchange Server accounts. Reducing the size of an offline Outlook Data File (.ost) might improve performance if you have deleted many items. This procedure does not delete any items saved on the computer running Microsoft Exchange Server.

  1. Delete any items that you do not want to keep.

  2. Open the Folder List view. At the bottom of the Navigation Pane, click the Folder List icon or press CTRL+6.

  3. In the Navigation Pane, right-click the Deleted Items folder, and then click Empty Folder.

  4. Click the File tab.

  5. Click Account Settings, and then click Account Settings.

  6. On the Data Files tab, click the data file that you want to compact, and then click Settings.

  7. Click the Advanced tab > Outlook Data File Settings.

  8. In the Outlook Data File Settings dialog, click Compact Nowand then click OK .

Note: You do not have to exit Outlook after you compact an Outlook Data File (.ost) file.

  • To delete an item from both the online and offline folders, select the item, and then press DELETE.

  • If you are using an Exchange account in Cached Exchange Mode, only the selected folder will be cleared from the offline Outlook Data File (.ost). The items on the server will be downloaded again to the .ost file on the next synchronization, if the folder is selected under Folder Options in Send/Receive Settings for the Exchange Server e-mail account.

  • When you use Cached Exchange Mode, public folders favorites are not synchronized by default. If you choose to synchronize public folders, the size of your offline Outlook Data File (.ost) might increase significantly.

The Mailbox Cleanup tool is used to view the size of your mailbox and individual folders. You can also archive older items to an archive Outlook Data File (.pst) and empty your Deleted Items folder.

  1. Click the File tab.

  2. Click Cleanup Tools.

  3. Click Mailbox Cleanup.

  4. Do any of the following:

    • To view the total size of your mailbox and any individual folders it contains, click View Mailbox Size.

    • To locate older items, select Find items older than n days, enter a number between 1 and 999, and then click Find.

    • To locate large items, select Find items larger than n kilobytes, enter a number between 1 and 9999, and then click Find.

    • To move older items in your mailbox to an archive Outlook Data File (.pst), click AutoArchive.

      Outlook Data Files (.pst) are saved on your computer in the Documents\Outlook Files folder. If you are using Windows XP, .pst files are saved in the My Documents\Outlook Files folder.

    • To view the size of your Deleted Items folder, click View Deleted Items Size.

    • To empty your Deleted Items folder, click Empty.

    • To view the size of your Conflicts folder, click View Conflicts Size.

    • To delete the contents of your Conflicts folder, click Delete.

If you delete items from an Outlook Data File (.pst), the file is automatically compacted in the background when you’re not using your computer and Outlook is running. You can also manually start the compact command immediately. It might take several minutes to compact an Outlook Data File (.pst).

  1. Delete any items that you do not want to keep.

  2. Open the Folder List view. At the bottom of the Navigation Pane, click the Folder List icon or press CTRL+6.

  3. In the Navigation Pane, right-click the Deleted Items folder, and then click Empty Folder.

  4. Click the File tab.

  5. Click Account Settings, and then click Account Settings.

  6. On the Data Files tab, click the data file that you want to compact, and then click Settings.

  7. Click Compact Now.

Note:  You do not have to exit Outlook after you compact an Outlook Data File (.pst) file.

An offline Outlook Data File (.ost) is exclusive to Microsoft Exchange Server accounts. Reducing the size of an offline Outlook Data File (.ost) might improve performance if you have deleted many items. This procedure does not delete any items saved on the computer running Microsoft Exchange Server.

  1. Delete any items that you do not want to keep.

  2. Open the Folder List view. At the bottom of the Navigation Pane, click the Folder List icon or press CTRL+6.

  3. In the Navigation Pane, right-click the Deleted Items folder, and then click Empty Folder.

  4. Click the File tab.

  5. Click Account Settings, and then click Account Settings.

  6. On the Data Files tab, click the data file that you want to compact, and then click Settings.

  7. Click Compact Now.

Note: You do not have to exit Outlook after you compact an Outlook Data File (.ost) file.

  • To delete an item from both the online and offline folders, select the item, and then press DELETE.

  • If you are using an Exchange account in Cached Exchange Mode, only the selected folder will be cleared from the offline Outlook Data File (.ost). The items on the server will be downloaded again to the .ost file on the next synchronization, if the folder is selected under Folder Options in Send/Receive Settings for the Exchange Server e-mail account.

  • When you use Cached Exchange Mode, public folders favorites are not synchronized by default. If you choose to synchronize public folders, the size of your offline Outlook Data File (.ost) might increase significantly.

You can use the Mailbox Cleanup tool, which allows you to view the size of your mailbox and individual folders. You can also archive older items to an archive Personal Folders file (.pst) and empty your Deleted Items folder.

  1. On the Tools menu, click Mailbox Cleanup.

  2. Do any of the following:

    • To view the total size of your mailbox and of individual folders within it, click View Mailbox Size.

    • To locate older items, select Find items older than n days, enter a number between 1 and 999, and then click Find.

    • To locate large items, select Find items larger than n kilobytes, enter a number between 1 and 9999, and then click Find.

    • To move older items in your mailbox to an archive Personal Folders file (.pst), click AutoArchive. The default folder for archive .pst files is c:\Documents and Settings\user name\Local Settings\ Application Data\Microsoft\Outlook.

    • To view the size of your Deleted Items folder, click View Deleted Items Size.

    • To empty your Deleted Items folder, click Empty.

    • To view the size of your Conflicts folder, click View Conflicts Size.

    • To delete the contents of your Conflicts folder, click Delete.

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If you delete items from a Personal Folders file (.pst), the file is automatically compacted in the background when you’re not using your computer and Outlook is running. If you want to immediately reduce the size of the file, you can force a compaction. The procedure to compact the data file might take several minutes.

  1. On the File menu, click Data File Management.

  2. Click the data file that you want to compact, and then click Settings.

  3. Click Compact Now.

Note:  You do not have to exit Outlook after you compact a .pst file.

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Reducing the size of the Offline Folder file (.ost) file may improve performance if you have deleted a large quantity of items. This procedure does not delete any items that are saved on the server.

  1. Delete any items that you do not want to keep, and then empty the Deleted Items folder.

  2. On the Tools menu, click Account Settings.

    The Account Settings command is missing.

    The Account Settings command is on the Tools menu in Microsoft Office Outlook 2007. If you are using an earlier version of Outlook, the following instructions do not apply. Use the Help that is included with that product. If the title bar of the program that you are using displays Microsoft Outlook Express, you are using a program that is not the same as Outlook. See Help in Outlook Express for assistance.

  3. In the list, select Microsoft Exchange Server, and then click Change.

  4. Click More Settings.

  5. Click the Advanced tab, and then click Offline Folder File Settings.

  6. Click Compact Now.

Note: You do not have to exit Outlook after you compact a .ost file.

  • To delete an item from both the online and offline folders, select the item, and then press DELETE.

  • If you are using an Exchange account in Cached Exchange Mode, only the selected folder will be cleared from the local .ost file. The items on the server will be downloaded again to the .ost file on the next synchronization, if the folder is selected under Folder Options in Send/Receive Settings for the Exchange Server e-mail account.

  • When you use Cached Exchange Mode, public folders favorites are not synchronized by default. If you choose to synchronize public folders, the size of your Offline Folder file (.ost) may increase significantly.

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