Emails Won't Stay Deleted

I use yahoo mail. My inbox is arranged with latest messages first. As I read and delete my mail, I often leave a particular email undeleted (for later review) and go on to the next email.

When I do that, it turns out that every succeeding email I "delete" does not actually get deleted.

Is there a way around this?

I am using Windows 7 and IE. Don't have smartphone. Sign-in page is as you have shown.

If I do not delete a particular emmail, clicking delete at the top of subsequent emails doesn't work (although I can X the boxes on those emails individually and they will delete)

Please don't lose any sleep on my little problem !