I had experience with networkx , but due to performance requirements i am thinking about trying graph-tool.

My main goal it to generate network graph for email communications , 

but i need to make it available online as interactive networks so i want to know if json serialization available?

I will use sigma.js http://sigmajs.org/ to render network graphs like this  :

I would be very grateful if i can have pointers for that.

Thanks

Phyo.