Microsoft Outlook 2010 (and earlier versions) is just a client: the meat of the program comes from the data your store in it: emails, calendars, contacts, etc. And all that data is stored in "PST
" files - and as you may already know, you can not only have multiple files for various accounts, you can also switch between PST files based on your needs. In this tutorial, we will show you how to password-protect access to Outlook by encrypting your sensitive PST files. Not that this isn't military grade encryption, but it will keep 99% of users from accessing your personal data and messages (and prevent accidental peeks!)
Start by opening Outlook 2010, if necessary choosing the PST file you want to protect (no need to do any of that if a) you don't know what a PST file is or b) have not setup multiple PST files).
From this point on, Outlook 2010 will not let you (or anyone) access the content of that file unless the correct password is supplied - make sure to remember or store somewhere a copy of the password, as Outlook doesn't come with a password recovery option for encrypted PST files. (Though you can find PST cracking software online, downloading and running that kind of software may be worst than having a third-party see the content of your emails, contact lists, etc.) To test your new security settings, exit Outlook 2010 and relaunch it - you should get the password prompt pictured at the top of this tutorial.
Tip: remember to also add password protection to your PST archives, not just on your main PST file. From the "Account Settings > Data Files" dialog and tab, click on the "Open File Location" button, and see what files are stored under your profile (should all be listed in the dialog) - and repeat above steps.
...follow the steps outlined above to delete the password you've setup: this time, enter the current password in the "Old Password" field, leave both other fields empty (blank), and click "OK".