I have looked in the PDF manual and on the in-device user guide but I cannot find a description of one of the e-mail screen icons.

I can figure out reply, reply to all, forward, trash, next and previous message... but what is the mountain with the clock in front? It appears active on some messages and not others.

I have a nasty feeling that this is going to be something really obvious and I am going to look foolish...
Thx