remove MAILER-DAEMON from a busy sendmail queue 

sendmail -bp | grep MAILER-DAEMON \ 
 | awk '{print $1}' | sed -e 's_\*$__gi'    \
 | awk '{print "find /var/spool/mqueue/ -type f -name *"$1 " -delete"}'


how to flush

sendmail -q -v