This small shell script removes all messages originating from a certain sender address out of the postfix mail queue.

#! /bin/bash
if [ "$1" == "" ]; then
  echo "please give e-mail address"
  exit 1
else
  emailaddr=$1
fi
for id in `mailq | egrep "[0-9A-F]{10} " | grep "$emailaddr" | cut -d " " -f 1`
do
  echo $id
  postsuper -d $id
done