Select the message to which you want to reply from the Inbox, and then click the Reply button on the Standard toolbar.
A message window opens with the To and Subject fields complete. Type the body of your reply in the message window.
Click the Send button to send the message.
Click the Sent Items folder to see whether the message was sent. (This works only if you have your email preferences set to send messages immediately.)
INTRODUCTION
When you reply to a message, the To field of the message you send is automatically addressed to the sender of the original message (you can add or delete recipients as needed) and the Subject line contains the original message's subject preceded by Re: to indicate that your message is a reply.
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Replying to All
If you receive a message that was also sent to other people, you might want to respond to the sender as well as to the other recipients. To do so, click the Reply to All button in step 2 and then type and send your message as normal.
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Saving to Draft
If you try to close a message window before you send it, you can save it in the Drafts folder. To access it later, click the Drafts folder in the Personal Folders list. You might need to expand the list of All Mail Folders.