To reply to a message

In the message list window, double-click a message to open it.
Do one of the following:

To reply to only the user who sent the message, click the Reply button on the message.

or
To reply to all users addressed on the message, click the Reply to All button on the message.

Note: You can achieve the same effect by right-clicking a message and selecting Reply or Reply to All.
(Optional) Customize your reply by adding a new text message, adding or deleting addressees, and/or adding or deleting attachments.
When finished, click Send to send the reply.