To reply to a message you received in Yahoo! Mail, first click on it to open it. When the message is open:
Depending on your “Message Actions” setting, you can see all, part, or none of the sender's original message in your Compose window.
To adjust these settings:
If you choose to include the message you’re responding to, you’ll see it in the Compose window with ">" symbols repeated down its left margin.
Type your reply. If you’ve included the sender's original message, you can place your cursor and type above it, below it, or even within the sender’s message itself—to respond to different parts of their email bit by bit. Click the cursor wherever you want to begin typing.
Tip: To make your reply easy to read, it often helps to hit Enter a couple of times to add space between lines. Here, we clicked the cursor after the question mark, then hit Enter twice to start the line that answers the question:
>for three years. Anyway, how's Mike doing?
Mike is great! I'll tell him you said Hi.
>We miss him. The house where he used to live is
Note: If you’re in the middle of composing a message and you need to stop, click Save Draft to the right of Send. This saves your uncompleted message in your “Drafts” folder. Come back whenever you want to finish it.
Note: Before you leave the computer, it’s a good idea to click Sign Out just below where it says “Welcome, yourname”. This way no one else gets to use (or abuse) your account while you’re away.