See How to Repair and Compact PST File when Encountered ‘Outlook cannot open the file'

Out of many advantageous features, one of the best features of MS Outlook is presence of Outlook PST file. Outlook PST file is a repository of your mailbox data on your local system. Whether they are emails, contacts, or any other information of your mailbox, all is stored on your PST file as well. However, the PST file has size limitation that varies according to the Outlook version. The early Outlook versions, until Outlook 2002, have storage capacity of 2GB, whereas the later versions until Outlook 2007 have improved it to 20GB.
Moreover, the latest Outlook versions Outlook 2010 and 2013 have increased the capacity of their PST file to 50GB.

Despite that, you may start facing performance issues with your Outlook as soon as its PST file reaches to or crosses over 2GB. If you ignore such issues, then you may face severe data loss due to PST corruption. Therefore, to avoid such situations, it is suggested to keep your PST file smaller by compacting it on regular basis.

Let us exemplify this fact. Suppose, you receive the following error message while starting Outlook 2007:

“Outlook cannot open the file ‘c:/..../outlook.pst’ run the inbox repair tool to resolve the issue”

This error message generally occurs when your PST file has reached to its predefined size that is 2GB. The oversized PST file gets easily corrupts and encounters any above mentioned error messages for the same. In such situation, it is recommended to repair it with the help of Outlook’s ‘Inbox Repair Tool’ before compacting the PST file.

The ‘Inbox Repair Tool’ gets installed with the installation of your Outlook in the form of scanpst.exe file and running it to repair corrupt PST file is not a difficult task. Therefore, run this utility and repair your PST file with it. Compact your PST file as soon as you are done with the repairing process with the inbuilt utility of Outlook.

For this you have to open Outlook and then click ‘File > Data File Management’ on the menu option. After that select your PST file from the PST file pane and then go to the ‘Settings’ tab provided above that window. This provides you Personal Folders Outlook window from where you can click the button labeled as ‘Compact Now’. In this way, with the help of this simple procedure you will be able to compact your PST file without much trouble.

However, there occur situations when this utility fails to do anything needful for users, as they do not find any big changes in the size of their Outlook PST file. In such situations, use of compact PST software is recommended. A professional compacting software shrinks the size of your PST file without causing data loss. An efficient tool generally extracts all the attachments and saves it in a separate folder. Some tools add themselves as add-in on MS Outlook application itself and are compatible with almost all Outlook versions. So, do not panic even if the inbuilt compact now utility does not solve your problem, instead use a professional compact PST software and overcome the performance issues.