Enable box "new messages"

Hi all,
I’m using RT 5, how can i enable the box “new messages”?

Thanks

If you want to enable this per user, go to Settings → preferences, scroll down to Ticket display section and enable “Notify me of unread messages”.
If you want to enable this globally edit your RT_SiteConfig.pm file to include the below line

Set($ShowUnreadMessageNotifications, 1);

Perfect!! Thanks a lot!!!