postinst is in couriergrey 0.3.2-5build2.
This file is a maintainer script. It is executed when installing (*inst) or removing (*rm) the package.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17  | #!/bin/sh
set -e
if [ -d /var/cache/couriergrey ]; 
then
  chown daemon:daemon /var/cache/couriergrey
fi
if [ -L /etc/courier/filters/active/couriergrey ];
then
  echo "Restarting couriergrey"
  filterctl stop couriergrey
  filterctl start couriergrey
fi
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