When I do the right-click / Share… then double-click on Mail from the list, the compose e-mail window comes up in the foreground. If I single click on Mail, the only thing I notice is that the name of the item selected changes from a white background to a blue background. The second click, even with a pause, brings Mail to the front.
I don't know what is causing the behavior you are seeing. Shut down and reboot and see if that helps.