It's very annoying to handle the source code of mails in the relative dumb internal source code viewer. Amongst lot others the complete lack of a search function is a pain everytime, I must analyze a source code. No! This isn't a request to integrate any sloppy search function into the source code window. Don't try to reinvent a wheel in a time of automobiles! Let the user define a viewer of it's own choice. It would be absolutely sufficient to open sources in the user defined text editor from the settings.
The wheel doesn't need to be reinvented, it's already there: You can create an action to open mail file(s) in an editor of your choice. gedit %F Personally I think that's good enough to avoid yet another exotic config option.
Or right-click the top-level message/rfc822 part and use "Open with" :) Marking invalid.
Sounds promising. I'm used to open source code via key Ctrl+U. My problem would be solved, when the standard choice choosen by mouse click would become the standard for Ctrl+U too.
Create an action as I suggested, and assign Ctrl-U as a shortcut.
@Holger: Finally understood, what you meant with 'create an action' Thanks a lot and Guten Rutsch