Thanks to RobertJ for supporting me with some code from "MIME edit".
after restarting my work on OpenX (formerly known as Gnome Open) today I came to a central question.
Is OpenX still needed in Thunderbird/Firefox 3. I installed the latest version today and everything (filetype association) seemed fine.
So please report your experiences especially with the new version of Thunderbird. Is the "problem" now fixed out of the box? Is Thunderbird your files correctly/like nautilus? Are there some features future versions of OpenX should include?
Contact me via Launchpad (http://launchpad.net/openx), on our blog (http://opencoding.wordpress.com/gnomeopen/) or on the Mozilla Thunderbird Addon page (http://addons.mozilla.org/en-US/thunderbird/addon/12523/).
Thanks for your help,