I have checked all emails that have been sent to me. There are no unopened emails, text messages or voicemail but there is an envelope icon on the device desktop indicating that there is an email waiting and unopened. What do I need to do???
I had this and it bugged me for ages, then in a flash of inspiration I realised that I had saved an unread message straight from the messages screen to the saved messages folder. The email disappeared from my messages when I deleted it after saving, but the icon stayed as the saved version was still "unread".