thread symbol??

[MATTY]

could anyone tell me what the envelope with a black dot in the middle of it is next to a "thread" it seems that threads i've posted or replied to have this and no-one elses seem to.am i doing something wrong or is it because i'm a beginner ????

[Mim]

I think it is to let you know which threads you have replied or subscribed to

Cheers,

Mim