As always, if you have new mail or system messages, the respective icons turn red in the menu bar.
Starting now, if you click on a red icon, instead of taking you away from the page you are looking at, it will instead open a popup dialog box that shows you what is new. You can then further click inside the dialog box to leave the page and go to the mail.
In the case of system messages, you can click the red "info" icon and it'll open the dialog and show you the new messages. You can then close the dialog box and continue with what you were doing.