no blue dot in unread mail

I was able to get blue dot showing email unread by selecting the email>Flag>Unread and blue dot appeared but this is only temporary. I need for all my emails that I haven’t read yet to show blue dot so I can distinguish between read and unread.

So how do you know you have new incoming mail that hasn't been read? What happens if you select an email then go to Message>Mark>As Unread? Do you get the blue dot then?

This has started happening to me as well on my macAir. When new messages come in they have the blue dot on the desktop computer, but not on the macAir laptop. ?? Yes, I can manually set it to show the blue dot, but that's not the point is it? Why has this changed? And how can I set it to do it automatically on incoming messages?

Mail>Preferences>Accounts>Advanced. Uncheck the box, "remove copy from server...."

I have this problem too, but the option that sig suggests doesn't exist on Mail>Preferences>Accounts>Advanced.

I just deleted my account as a POP3, and then set it up as an IMAP per my hosting's suggestion and now have the same problem. No blue dots next to the unread emails. It seems no one answered this. :-(