The Owner or Administrator of a Yahoo! Small Business account with Business Email can grant administrative privileges to any of the account's Business Email users who access email via Yahoo! (POP-only users don't have Yahoo! IDs, and therefore cannot sign in to Yahoo! to access the Email Control Panel.)
To make a user an administrator:
Access the Email Control Panel.
Click "Edit User" under the name of the person you'd like to grant administrative privileges.
Email Control Panel - Edit User Link
Click the "Make (name) an email administrator." checkbox, and click the Save button.
Email Control Panel - Edit User Page - Administration Privilege Checkbox
Tip: Don't see this section? If the user has a POP-only Business Mail address, the user cannot be an Administrator because there is no Yahoo! ID associated with their email account.
Enter the Yahoo! Security Key and click the Continue button.
Verify Security Key Page
Note: If a Security Key has not already been created for the Yahoo! ID you are signed in with, you will be prompted to create one rather than entering an existing a Security Key.
You will receive a confirmation message, "This user in now an administrator."
This user can now create, edit, and delete email addresses and assign administrative privileges to other email users. The new Administrator can learn more about managing Business Email at Yahoo! Business Email Help.