If Exchange System is your mail system in company, I think the client almost install Outlook Application as mail client to send/receive mail from/in Internet or Intranet.
If use Outlook application, the Exchange mode almost is set and mail format define PST file. In general, the PST is Microsoft private format so that just can open it by Outlook.
Whether has alternate method to view Outlook Mail but never open Outlook Application?
By Google, I find out an utility “
Kernel Outlook PST Viewer” can help me to finish this target.
Down/Execute it from the Official Web Site and begin to launch the installation wizard

Click
Next > button

In
License Agreement page, choose I
accept the agreement option next to click
Next > button

In
Select Destination Location page, click
Next > button if we don’t want to change the default path.

In
Select Start Menu Folder page, click
Next > button if we don’t want to change the program’s shortcut.

In
Select Additional Tasks page, click
Next > button after we decide to create a desktop/quick launch icon or not.

In
Ready to Install page, click
Install button if we have already confirmed the settings.

When complete installation, select
Launch Kernel Outlook PST Viewer check box and click
Finish button

Click
Browse button for selecting source PST file

Select one PST file from Folder Explorer

In loading PST process…

So do that we can view the PST content now.

Click a folder and one mail so that the content will be viewed now.