When you create a new Business Email address and select the option "Using Yahoo! and/or another mail program, such as Outlook Express," your friend or employee will need to sign up for their own Yahoo! ID that acts as a user name to access the Business Email account, or use an existing Yahoo! ID they already have.
We strongly advise against you signing up for multiple IDs on behalf of the users you wish to give Business Email access to, as creating a number of Yahoo! IDs may result in these IDs being flagged for suspicious activity. Instead, we recommend allowing these users to follow the instructions in the invitations they receive and either create their own Yahoo! IDs or use their existing Yahoo! IDs.