2017 News Moodle 3.2
To send new messages, click the message icon in the menu bar or Messages in the User menu.
If you click on a user's name anywhere in Moodle, you will come to the person's profile page, even there is a link to messages.
You can create a contact list to easily find people you often contact. Here you can also search for a new contact in the courses that you are eligible for. Later you can click the name to block or remove the contact.