右上角出現小信件符號?

[～笨咪小孩～]

請問我這幾天突然發現右上角出現一個小信件的小圖案,怎麼用他都不會不見
請問那是什麼東西呢

[ezza]

this is an icon to remind you have unread email in mail box.
go to 'mail' and read them and the icon will be gone