You can Manage these easily.
Yes Outlook .PST files may be stored in one of three states: unencrypted, password protected, or encrypted.
Some step behind it.
1. Setting a password for your .PST file in Outlook 2010:
To password protect your .pst file in Outlook 2010, click on Outlook's Account Settings button, then "Data Files" and "Change password." You will be prompted to change the password for the PST file. Once the password is set, it will have to be entered each time Outlook is started.
Remember, password protection does not encrypted the .pst file, So you need to use a an Outlook viewer or PST viewer. You can find many outlook viewer in the web.