No. When a Business Mail administrator creates an email address, the administrator chooses whether to give the user web and POP access to the new email address, or POP access only. If your invitation included only POP instructions, you have been invited to set up a POP-only email address. This means you can access your email only via a POP-enabled mail program (such as Outlook or Thunderbird). You cannot use the Yahoo! Mail interface to manage this address.
To activate your email address, you'll need the POP settings included in your invitation and the password that your email administrator will provide for you. Learn more.