The subjects look like they are links – they are blue and the mouse pointer turns into a hand.
Examples are “Delivery Status Notification (Failure)”, “Email Feedback Report (Complaint)”, “Undeliverable: [Forum name] Topic name”.
I’ve just noticed that ones in the form “Re: [Forum name] Topic name” do work as links.
I see a bit of this too. Everything is in <a> tags, but some have no href.
I don’t have examples like your first batch, but I think I’d expect those to pop up the email details the way the Rejected list does.
I do have a few “Re: [Forum name] Topic name” that don’t link to anything because that topic has been deleted.
At the least, it would be nice if items with no link destination weren’t rendered as links.