+
+ my $classnum = $opt{'to_contact_classnum'} || '';
+ my @classes = ref($classnum) ? @$classnum : split(',', $classnum);
+ # traditional behavior: send to all invoice recipients
+ @classes = ('invoice') unless @classes;
+ @to = $cust_main->contact_list_email(@classes);
+ # not guaranteed to produce contacts, but then customers aren't
+ # guaranteed to have email addresses on file. in that case, env_to
+ # will be null and sending this message will fail.
+