Mail user account can be created on the specified domain either by Plesk Administrator or by Plesk client. To register new mail account in Plesk database, it is enough to specify some general setup information, namely: the domain ID where the mail account will be registered, and the mail account name.
In addition, you can specify various mail account settings (all of them are optional):
A mail account can have all these settings specified, or it can hold just some of them. You can specify these settings when creating a mail account or later (they can be set using the set_prefs operation).