Hi Gary,
Yeah, I'm seeing the same behavior: where there's no preview pane, it's not possible to open a message. Interestingly, it works in 11.1. (Which I have no my iPhone.) I'll log the issue and let the devs know. For now, any chance you can use a preview pane? That's working just fine.
Derek Curtis
COO
SmarterTools Inc.
www.smartertools.com