MS Outlook uses Personal Storage Table or PST file to store emails, contacts, data and other information of user profile. The data in the PST file occupies respective space which are further retrieved and used. Sometimes, it happens that Outlook does not automatically delete white or unused space left after removal of any item from the PST file. That unoccupied space remains unused and increases the PST file size considerably. To overcome this space complexity issue, you can implement PST compaction technique. If you compress PST file in Outlook, it not only eliminates deleted items space but also recovers room on your hard disk.

To converse space on the hard disk, you can delete unwanted items from the various .PST folders and then compress them to reduce their size. When you delete something from each folder in Outlook, the deleted items are not permanently deleted rather they are shifted to Deleted Items folder. When you compact the file, Outlook removes all extra space from the folders and shrinks the size.

To be compacted, a file must meet the following requirements:

• The file must be 16 KB or larger.

• The file must have at least 16 KB of space freed since the last time it was compacted.

How to Manually Start PST Compaction

• On the File menu, click Data File Management.

• Click the personal folders (.pst) files that you want to compact, and then click Settings.

• Click Compact Now, click OK, and then click Close.

Apart from manual compaction, you can ideally use commercial compaction techniques that successfully  compact and compress pst file and removes the unused space. Kernel for PST Compress and Compact is a dexterous tool that is exclusively designed to compact PST file. Supporting PST file created in all versions of Outlook, this software is capable of compressing multiple files in one cycle.