From the Participants page
Go to the course Participants page. View the profile of the user you want to contact. Select Message, compose your message, and select Send message.
More on the the Participants page
If you do not see the Quickmail block, a site Administrator or Teacher with editing permissions needs to add the Quickmail block to the course.
To compose a message, navigate to the course where you would like to send the message, locate the Quickmail block, and then select Compose New Email.
On the composition page, view previously created draft messages, view a history of sent messages, filter users by role, or select recipients that you would like to email.
Select multiple recipients at once by holding down the Ctrl key.
Once you select message recipients, add attachments and compose your message.
Select Send Email to send your message.