Couple of scripts I used while cleaning up a mail server. I’m sure they can be improved, and the last one is quite specific to my own requirements, but I’ll put them here anyway.

Move emails with a particular subject from the hold queue to the deferred queue:

#change directory to postfix's queue directory#
cd $(postconf -h queue_directory)/hold
#loop over queue files
for i in * ; do
# postcat e file, grep for subject "test" and if found
# run postsuper -d to delete queue'd message
postcat $i |grep -q '^Subject: test' && postsuper -H $i
done

Delete emails in the hold queue that are being sent to a recipient that has already recieved an email (is in the mail log) or duplicate emails (with the same email/subject):

cd $(postconf -h queue_directory)/hold
#loop over queue files
NUM=0
for i in * ; do
   if [ -f "$i" ]; then
       IDENT=$(postcat $i | grep -A 1 "To:")
       RECIPIENT=$(postcat $i | grep "To:" | cut -c 5- )
       if grep -q "$RECIPIENT" /root/postfixtmp/logs/mailsent.log; then
           echo "* already sent to $RECIPIENT, deleting $i " | tee -a /root/postfixtmp/queueclean.log
           echo $IDENT | tee -a /root/postfixtmp/queueclean.log
           NUM=$[NUM + 1]
           postsuper -d $i
           echo "----" | tee -a /root/postfixtmp/queueclean.log
       else
           for o in * ; do
              if [ -f "$o" ]; then
                  if [ $o != $i ]; then
                     CURRENT=$(postcat $o | grep -A 1 "To:")
                     if [ "$CURRENT" = "$IDENT" ]; then
                        echo " duplicate email, deleting $o *" | tee -a /root/postfixtmp/queueclean.log
                        echo $CURRENT | tee -a /root/postfixtmp/queueclean.log
                        NUM=$[NUM + 1]
                        postsuper -d $o
                        echo "----" | tee -a /root/postfixtmp/queueclean.log
                     fi
                  fi
              fi
           done
      fi
   fi
done
echo "Deleted $NUM emails" | tee -a /root/postfixtmp/queueclean.log