How to build a Apple Mail bundle with Xcode?

I know that mail.app plugins aren't offically supported by Apple, nevertheless there is the possibility to execute plugins and some are doing that by using python-applications (e.g. http://eaganj.free.fr/weblog/?post/2009/开发者_StackOverflow07/14/Demystifying-Mail.app-Plugins-on-Leopard).

But because Apple is giving the possibility to use a great tool like Xcode, I would rather work with that tool. My question is: What type of project do I have to choose and which settings have to be done to create a mail-plugin with Xcode?

Only tutorial I've found is available here: http://eaganj.free.fr/weblog/?post/2009/07/14/Demystifying-Mail.app-Plugins-on-Leopard by James R. Eagan