The name and address configured for the account creates the default mail identity. When Mail Identities is enabled, users can create additional mail identities to manage different roles. Each identity includes a name and email address. Users can set up mail identities from their account Option tabs
Note: To let users create
email addresses for mail identities, on the Preferences tab, check Allow sending email from any address. If this is not enabled, users can only select from email addresses (something@yourdomain.com) or aliases (somethingelse@yourdomain.com) that you have configured.