How to compact data (pst/ost) files in Outlook?

For a long time Microsoft Outlook’s data files (pst/ost file) may have taken up huge space in your computer. Apart from mailbox cleanup by emptying deleted items folders, you can release the occupied space by compacting data files. This article will show you how to compact data file (pst/ost data files) in Microsoft Outlook.

The following steps will guide you to compact data (pst/ost) files in Microsoft Outlook.

Step 1: Open the Account Settings dialog box:

1. In Outlook 2007, please click the Tools > Account Settings;
2. In Outlook 2010 and 2013, please click the File > Info > Account Settings > Account Settings.

Step 2: In the Account Settings dialog box,

1. Click the Data Files tab;
2. Click to highlight a data file that you will compact later;
3. Click the Settings button.

Step 3: If you select a pst data file in Step 2, please skip to the Step 4.

If you select an Exchange account’s ost data file in Step 2, the Microsoft Exchange dialog box will come out. Please check the Use Cached Exchange Mode box and then click the Outlook Data File Settings button (or Offline Folder File Settings button in Outlook 2007) on the Advanced tab in this dialog box. But if the selected ost data file is not from the Exchange account, please skip to the Step 4.

Step 4: In the new popping up dialog box, please click the Compact Now button.

Step 5: Click all OK buttons and Close button.