Don't want co-workers snooping on your Outlook mail? Setting a system password to lock your entire machine remains the best tactic, but for added security you can also set a password on the Outlook file itself.
Microsoft's Crabby Office Lady blog highlights a longstanding but often-ignored feature of Outlook for users accessing POP accounts and storing their mail in a PST file. The process, as explained on Microsoft's support site, is pretty straightforward -- but remember not to save the password on your password list if you want a maximum degree of protection.
Of course, for that to be an effective strategy you need to pick a good password in the first place -- and don't forget it, as if you do, the PST file will be pretty much irretrievable. Even if you're happy with your level of Outlook security, improve your experience with the top 10 Outlook boosters and our guide to speeding up Outlook.