When you register with Yahoo, you automatically create a Yahoo! Public Profile page for each Yahoo ID and alias that you establish. You can create up to five different profiles with different aliases for a single Yahoo ID.
Yahoo Profiles gives you the ability to post personal information about yourself including your name, city and state, age, and email address, to name a few. All of this information is optional and all of the information that you choose to enter will be available for anyone to see. You can use any alias you have created on a variety of Yahoo! services including Yahoo! Chat, Clubs, Classifieds, Messenger, Games, and Message Boards.

But a regular profile does not act as forwarding e-mail address. this means you will not be able to get receive emails sent on your alias instead of your ID. Maybe you have different categories of contacts—like Personal and Business—and you’d like to separate the addresses you use with each. Having two accounts is not comfortable. Maybe you don’t like your old address anymore and you are stuck with it cause you can not change your username and you do not want to start a new account cause you would lose your old contacts. In this case you can create an extra mail address.

An extra mail address is a special kind of profile that you can use specifically with Yahoo! Mail.
It is a second Yahoo! Mail address that you can use with your existing Yahoo! Mail account. It’s not a separate Yahoo! ID, and it’s not a separate Yahoo! Mail account. It’s just another address you can use to send and receive email, and any messages you get go into the same Inbox you already use.

If you already have other profiles set up, you can choose to turn one of them into your extra mail address. At this point the extra address will act as a valid email address and will have all the features of a regular profile. You will have a single inbox for your yahoo email address and the extra address and you will be able to select the from one of them as sender address address when you compose a new email.

To create an extra mail address

• Login into your email account
• Click Options in the upper-right corner of your Mail page and select Mail Options.
• From the list on the left, click Accounts.
• The second section of this page is “Extra Mail Address.” Click Get Started and follow the instructions to create an extra mail address.