+no_search_fields - arrayref of additional fields that are not search parameters
+
+alternate_form - subroutine that returns alternate html for the initial form,
+replaces msgnum/from/subject/html_body/action inputs and submit button,
+not used if an action is specified
+
+post_search_hook - sub hook for additional processing after search has been processed from cgi,
+gets passed options 'conf' and 'search' (a reference to the unfrozen %search hash),
+should be used to set msgnum or from/subject/html_body cgi params
+