Your mailbox password is required to access your email account using MailSender or a POP email client. You can reset this password from the "Manage Email" page within your Domain Control Panel:

1. Visit your Business Control Panel (if you haven't entered your Yahoo! ID and password, you'll be prompted to do so here).
2. Click the "Domain Control Panel" under the domain you'd like to update.
3. Click the "Manage Email" link.
4. Follow the instructions on the page to reset your mailbox password.