safari to open external links in new window

I like safari to open links in new _tabs_ in general. I.e. when I do a search, I want results I click to open in new tabs in the same window. This allows to have multiple windows with multiple tabs and have them grouped by topic. when I click on a link i an email, safari (on OS X) somehow (randomly?) chooses an open window and opens the link as a new tab in it. sometime it picks even a minimised window, although there are others visible on the same space. to be clear: I want the new window when the action is triggered from external application (e.g. Mail, etc.). Within Safari I'd like to stick with the default behaviour. I tried the Safari Settings -> Tabs -> Open new pages in tabs instead of windows setting (all of them), but this does not give the expected result. it is general for all. Also google did not know a satisfying answer, so I am asking here. Any help is appreciated.