The client list is equipped with an internal communication system. Users invited to the list can communicate using a chat system similar to WhatsApp or facebook. To use the system click at this icon in the right top corner:

You will see the chat window appear on the right side of the screen:

If the user is active you will see the status as a green circle. You can click the name and start chatting with a specific person:

You can open as many chats as you like. If a user is not active he will receive an email that someone is trying to reach him, and when he comes back he can read all the messages