Preferences are miscellaneous session information. They include by default the fields:
email
fax
phone_night
fax_order
email_copy
The field p_nickname acts as a key to select the preference set. You can
change the values that are included with the preferences parameter: [userdb function=set_preferences preferences=``email_copy email
fax_order fax'']
or in catalog.cfg:
UserDB default preferences "mail_list email fax_order music_genre"