+=item invoicing_list_addpost
+
+Adds postal invoicing to this customer. If this customer is already configured
+to receive postal invoices, does nothing.
+
+=cut
+
+sub invoicing_list_addpost {
+ my $self = shift;
+ return if grep { $_ eq 'POST' } $self->invoicing_list;
+ my @invoicing_list = $self->invoicing_list;
+ push @invoicing_list, 'POST';
+ $self->invoicing_list(\@invoicing_list);
+}
+