The icons in your shot are Thread, Starred, and Attachments. See my screenshot, and click the red-circled icon, and UNcheck Thread, Starred, and Attachments. Thread means you are showing conversations, not just individual posts. Starred means Important (to you). Attachments will appear next to a message that has one or more of them.

You might want to go into the Menu Bar's (press Alt if you don't see the Menu Bar on your screen; it will pop up) View, then Sort by, then click Unthreaded. That will get rid of the Thread icon, too.

I know what threading is, and I have it turned off. This in NOT that. The yellow icon is not the one for stars or attachments either. Both of these are in the 'Subject" column, NOT in the thread column, nor in the "Star" column.

Better screenshot showing the location is attached.

Sorry. Now I understand your question. The left arrows mean that you have replied to the message. Rights mean you have forwarded. Yellows mark new unread messages; bolded subjects are unread ones.

Hope this helps.