Does anybody know..
 

...the exact meaning of ALL the envelope symbols at the beginning of the threads? The black dot, the rays, the envelope open, closed, red, gray, yellow, the lock... any more existing?
Who really knows that?

I'm sure the black dot means you've posted in that thread

Ah, there at the bottom of the forum page is a little explanation.
But together with the dot I was confused. Now I know better. TY

If you look at the bottom of each forum there is a guide that tells you what different envelopes mean.

Yes a dot does mean you have posted to that thread previously.

Yellow envelopes are new threads.

Orange evelopes have had at least 15 replies or 150 views.

Gray envelopes indicate no activity since you last visited.

Hope that helped!

TY hun.