Unzip Dovecot emails crypted using zlib plugin

dovecot-unzip.sh

#!/bin/bash
# Unzip /var/vmail
find /var/vmail/ -type f -regextype egrep -regex '.*S=.*W=.*' | while read -r file; do
if [[ $(head -c11 "$file") == "Dovecot-LZ4" ]]; then
doveadm fs get compress lz4:0:posix:prefix=/ \
  "$file" > "/tmp/$(basename "$file")"
  if [[ -s "/tmp/$(basename "$file")" ]]; then
    chmod 600 "/tmp/$(basename "$file")"
    chown 5000:5000 "/tmp/$(basename "$file")"
    mv "/tmp/$(basename "$file")" "$file"
  else
    rm "/tmp/$(basename "$file")"
  fi
fi
done