With dovecots zlib plugin, it's possible to have compressed mails in the users maildir.\\

I've written a script to compress all mails on my mailserver:\\

#!/bin/sh\\

compress_maildir () {\\
cd $1\\
DIRS=`find -maxdepth 2 -type d -name cur`\\
for dir in $DIRS; do\\
　　echo $dir\\
　　cd $dir\\
　　FILES=`find -type f -name "*,S=*" -not -regex ".*:2,.*Z.*"`\\
　　#compress all files\\
　　for FILE in $FILES; do\\
　　NEWFILE=../tmp/${FILE}\\
　　#echo bzip $FILE $NEWFILE\\
　　if ! bzip2 -9 $FILE -c > $NEWFILE; then\\
　　echo compressing failed\\
　　exit -1;\\
　　fi\\
　　#reset mtime\\
　　if ! touch -r $FILE $NEWFILE; then\\
　　echo setting time failed\\
　　exit -1\\
　　fi\\
　　done\\
　　echo Locking $dir/..\\
　　if PID=`/usr/libexec/dovecot/maildirlock .. 120`; then\\
　　#locking successfull, moving compressed files\\
　　for FILE in $FILES; do\\
　　NEWFILE=../tmp/${FILE}\\
　　if [ -s $FILE ] && [ -s $NEWFILE ]; then\\
　　echo mv $FILE $NEWFILE\\
　　mv $FILE /tmp\\
　　mv $NEWFILE ${FILE}Z\\
　　else\\
　　echo mv failed\\
　　exit -1\\
　　fi\\
　　done\\
　　kill $PID\\
　　else\\
　　echo lock failed\\
　　exit -1\\
　　fi\\
　　cd - >/dev/null\\
done\\
}\\

compress_maildir /home/user/.maildir/\\
chown -R username:users /home/user/.maildir/\\
If using this script, please do it after an backup/copy of the maildir, the script is far away from being perfect :-)\\

If the Script is rerun, it checks the files for a Z at the end of the filename, so the file isn't recompressed.\\

With compressed mails i saved ~25% of space.\\