Why does not the midi output work with sylenth1 and zebra2 in sonar x3? Albino and Nova Bass Station works fine? On sylenth1 and zebra2 the enable midi output function is greyed out though i enabled it?

I do not know the capabilities of the synths mentioned. The Cakewalk VST scanner must have determined the synths did not have the capability and set the generateEvents key to 0 in the VST registry for those plug-ins. It does not matter whether the "Enable MIDI Output" is checked or not if the generateEvents key is set to 0.

Saw your post and thought I would ask this question. What is the purpose of midi out on a softsynth? I've never found a use for it. Am I missing out on something?

Not all soft-synths output MIDI, Sylenth is one of the ones that doesn't.
 
Don't have Zebra2 but based on your experience would say it probably doesn't either.
You could always post a feature request with Urs.

wep342
Saw your post and thought I would ask this question. What is the purpose of midi out on a softsynth? I've never found a use for it. Am I missing out on something?

If I'm not mistaken it can allow you to capture realtime changes made in the plug-in GUI using your mouse while recording a track; without having to map a controller to that gui knob/fader. For example if you're are tweaking filter settings with your mouse.
 
Maybe someone who actually uses this can shed more light on practical applications.
 

wep342
Saw your post and thought I would ask this question. What is the purpose of midi out on a softsynth? I've never found a use for it. Am I missing out on something?

As The Steven said you can make realtime captures or record the midi notes from an arpeggiator.

And there are many VSTs that can be controlled (some of their features) by MIDI from other VSTs.
Like in making vocoder -type of things etc.