sendmail init script does not kill clientmqueue flushing deamon, there's a sm-client.pid file in /var/spool/clientmqueue. bye
sendmail-8.12.7-r1 has been released into portage with an updated /etc/conf.d/sendmail and /etc/init.d/sendmail which shuts down the clientmqueue daemon as well as the mta. Thanks for the heads up.