Removing an extra mail address is just as easy as creating it. Here's how:

1. Click Options in the upper-right corner of the page and select Mail Options.
2. Under “Management”, click Mail Addresses.
3. Click on the extra address you want to delete.
4. Click Delete.

When you've removed your extra mail address, email messages sent to that address bounce back to the sender.

When you delete an extra mail address, Yahoo! removes it, but still keeps it as a profile to your Yahoo! ID. A profile is an ID that's used to protect your Yahoo! ID. You can sign in with a profile to Yahoo! Games, Yahoo! Message Boards, or Yahoo! Chat without exposing your Yahoo! ID.

If you want to permanently delete your extra mail address and not keep it as a profile, you'll need to delete the profile.