What kind of Compression or Encryption do I want for Outlook's .PST files?

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Summary: Microsoft Outlook allows you to compress and/or encrypt your PST file. We'll look at what the options are, and when you might choose them.

In an earlier article I discussed compacting an existing .PST, and creating additional .PSTs. One thing I didn't talk about was what kind of encryption or compression to select. In most cases the default is fine, but understanding the differences may help you select something more appropriate for your situation.

When you create a new .PST, Outlook offers you three different types of encryption: none, compressible, and high.

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No Encryption means just that. Outlook will store your email in such a way that anyone with access to your .PST and notepad will be able to view your mail. It won't be pretty because it'll be intermixed with Outlook's control information and anything in HTML will have all of the HTML tags intermingled. But it will be easily visible.

Compressible Encryption will obfuscate the data in your .PST such that simple tools like notepad will see only garbage. In fact, it'll take some hacker's tool to actually decrypt the data. The term "Compressible" is used because the type of encryption used does not defeat the techniques used by programs such as ZIP, or even the built-in compression that's available on some Windows file systems.

High Encryption uses a stronger form of encryption that is more difficult to hack. It's also potentially more time consuming for Outlook to read and write. And as you might guess, this form of encryption does not compress well if at all. You can still attempt to compress a copy of your .PST for backup if you like, but it's not likely to get much smaller if at all.

So the bottom line is it depends. If you don't care that your .PST might be readable by someone or perhaps you use other forms of security to prevent access, then perhaps No Encryption is right for you. If you're storing sensitive data or have other reasons to be concerned, then perhaps High Encryption is best.

As for me I leave it at the default: Compressible Encryption. I do occasionally want to be able to compress my .PSTs (they do get big), but I'd at least like to keep the casual browser from easily reading my mail.

Article 140 | Posted January 16, 2004