Mail close

You're referring to the "close" button on an email!

The "close" button on an email is typically represented by an "X" or a "Close" label. When you click on it, the email window or tab will close, and you'll return to your email inbox or the previous screen.

If you're looking to close an email thread or conversation, you can usually do so by clicking on the "Close" or "Mark as Closed" button, which may be located at the top or bottom of the email conversation. This will help keep your inbox organized and prevent further responses from being added to the thread.