If you have MyChat Server (10 connections) installed in your local network or company you can use it to exchange messages.
You can setup your own Mychat server. If your company has limited internet access you can not use Skype on your network. But you can use the Mychat server with SSL encryption for the transmitted messages. There are different forms of chat tools you can choose from.You can for example use a webchat and place it on your website. This allows visitors to chat to your employees through your website. You can also use an audio, video chat which allows you to have audio or video calls.
Download a free version of corporate messenger My Chat.