E71 - flashing envelope but not a message, how to get rid of it

I have a 'flashing envelope' flag on my E71 that I just can't clear.
It's not indicating an unread text message as I have delete *all* my
text messages.

The flashing envelope is positioned *next* to the one for text
messages I think as, at one time, I had two of them.

I can't find anything in the user manual about it so can anyone tell
me what this flashing envelope indicates, it's driving me crazy at the
moment.

--
Chris Green