Yahoo Mail has a feature that allows users to save a copy of the messages that are being sent in Sent folder. This is useful when you want to have a backup of important emails mailed from your account. Instead of adding your email in cc or bcc list you can use Save a copy of message feature.
Steps to enable save a copy of messages
Step 1: Login to your Yahoo Mail account.
Step 2: Click Settings icon and select Mail Options from the list.
Step 3: In the Mail Options screen, navigate to Sending Messages section and mark the check box with caption as “Save a copy of the message in the Sent folder”
Step 4: Click the Save button available next to “Customise how you read and send your email“.
Now whenever you send an email, a copy of the message will be stored in the Sent folder.