It means the account has new mail you have not seen.

Hi Matt, Thanks for responding. What you suggest is what I originally thought.

There is in fact a yellow dot (per your answer) that appears over the envelope icon next to any inbox with unread mail. (see screenshot 1) That yellow dot goes away when I read unread mail. But the yellow dot I'm concerned about appears over a different icon - an envelope with a lock on it. (see screenshot 2) The locked-envelope icon is labeled with my email address, and when I click on that, I see various information about my account displayed. (see screenshot 3)

Even if I've read all the messages in all my inbox, that other yellow dot (on the locked envelope) never seems to go away. Clicking on the various options in Screenshot 3 doesn't help.

So I'm still mystified.

Usually. I have the account expanded, so I see folders. If a mail account get new mail then I see the yellow dot on the folder that has new mail.

BUT, if I collapse the mail account, so I only see the mail account name folder - all the folders are not displaying - I will now see the yellow dot on the mail account name folder. It is telling me there is new mail in that account.

re :Even if I've read all the messages in all my inbox, that other yellow dot (on the locked envelope) never seems to go away.

That is a bit weird.

Do you have the following settings:

• View > Folders > All
• View > Threads > All

If different then tell us what settings you are using.

Is the mail account displaying all folders?

Do you see the same when you restart in Troubleshoot mode/Safe Mode? Menu icon > Help > Troubleshoot Mode click on 'Continue in Troubleshooting Mode'