Lowengard,

I am talking about http://en.wikipedia.org/wiki/Requirements_management

It is a stage when you collect and organize client wishes before creating a project plan.

If "requirements management" sounds confusing you can replace it with "project collaboration".

The problem is that most project management services provide you with task tracking but there is no easy way to write down the origin of these tasks.

Here is a simple example of the problem: there are 100 projects you discussed with your clients via email. Some projects have 100+ emails with various information. Now imagine you need to refer to some specific agreement you made with a client 3 months ago. I guess you will agree that it is not easy to do. You need some way to keep this information organized.

The list I provided contains equally important properties of the system I need.