Secrets, a clever little System Preference Pane that makes tweaking “hidden” features of Mac OS X easy (see earlier Hawk Wings post for more), has been updated to 1.0.6 and is now compatible with Snow Leopard.

Secrets provides easy assess to many of Mac Os X’s settings that you can otherwise only change by messing around in Terminal with long command strings, which is not everyone’s cup of tea.

It includes tweaks for many Mac core and a wide range of third-party apps. The most popular tweaks across all the apps are listed separately as well.

Of course, here we are most interested in its options for Mail.app:

Secrets Mail Preferences

As you can see from the screenshot, Secrets allows you to

• specify a default BCC email address
• force Mail to display messages in plain text
• set the Bundle compatibility and enable bundles
• enable and disable the data detectors
• switch the new (annoying) Snow Leopard behaviour of including names in copied email addresses on and off
• set a sent mail sound
• specify a minimum for HTML messages and a preferred text encoding
• request read receipts
• set the interval for refreshing Mail’s RSS feeds
• Decide whether to display attachments inline or not.

And more.

Some people will think of it as a hack and might be wary. However it comes with the reassurance that Alcor, the developer also (once) behind Quicksilver, is its creator. That’s a strong pedigree.

Secrets is freeware and available from the Blacktree web site .

UPDATE: I read on TUAW that the Blacktree site is overloaded. Secrets is also available from the app’s page on code.google.com.