Leopard 10.5 update: Mac OS X 10.5's Mail.app requires bundle version 3 or greater. See comment below.
I've been fiddling around to get GrowlMail to work with the latest version of Growl. Installing the GrowlMail bundle went fine, but the preference pane doesn't show up in Mail, and Mail doesn't show up as a registered application in Growl.
It turns out you need to run the following 2 commands in your favourite shell:
defaults write com.apple.mail EnableBundles 1
defaults write com.apple.mail BundleCompatibilityVersion 2
- Mac OS 10.4.8 Mail v2.1 (752/752.2)
- Growl v0.76
- Orig.: http://forums.cocoaforge.com/viewtopic.php?p=70206