You can send messages to other players. These messages will be sent when the host runs, and receivers can read them next turn.

Choose races to send message to, or U to send a universal message (to everyone). You'll be placed in the message editor. Write your message; F10 sends, ESC cancels.

Reference

Keys:
W from race screen.
This is a testing version.
It may be incomplete, and have more bugs (or features) than the public live version at planetscentral.com.