What does Email with an exclamation point inside triangle mean

Tarasuef wrote:

I have an old yahoo email account that I read on my apple email it's still working but this triangle is sitting beside my email address on the left hand side of Mail. I'm still getting email but I'm concerned that maybe I'm not getting all of my email and I don't know how to clear that triangle. Should I go directly to my yahoo.com mail log in and do something there?

Click on your "exclamation point inside triangle" and see if resolves...

Quit the mail.app and relaunch holding the Option key and compare your results...

No resolve— reboot the Mac and try again

If no insight try the Mail>Window >Connection Doctor

Use Connection Doctor in Mail on Mac - Apple Support

With Yahoo that means issue connecting to server. Whenever I see this I cannot receive any mail so not sure why you are still able to receive. Like already suggested try closing out mail app and restart mail. It might clear out or wait for awhile and try again.