Meaning of "Blue dot" in Mail's "Sent" Folder?

[Todd's keyboard]

A Facebook friend just asked this question about the meaning of a blue dot in Mail's "Sent" folder:

"what does the blue dot mean next to a message in mac mail sent folder? I know what it means in the inbox, it means unread. but what about in the sent folder?"

A follow-up points out:

" if I right click on a message and say MARK AS UNREAD the blue dot comes up. I don't understand how a message in SENT could possibly be UNREAD though."

thanks, Todd's keyboard

[Zoidberg]

That happens to me sometimes too. Also, occasionally, a read message will get marked as unread when I move it (either to a sort folder or to the trash).

Glitch in the system.

[modelamac]

I've seen that occasionally. I call it an aberration, and move on.

[tenders]

Wonder if the shortcut for marking read/unread (command-shift-U) sometimes gets hit unconsciously.