Messages - Changing the Message Mode
Users have the option of switching between the Single Message dialog box or the Split Message Mode dialog box. Click on the Message Mode button to switch between dialog boxes.

After sending a message, the dialog box will automatically close.

The Single Message Mode offers you the option of viewing the message history between you and the other user. Click on the History button to view message history.

A message may be sent to multiple users by clicking the More button, and then clicking on the Multiple Recipients button.