Compresses email in maildir format

dovecot-maildir-compress.sh

#!/bin/bash

# Enable zlib in Dovecot alongside automatic writing of new emails in gzipped format

echo '# Enable zlib plugin for reading/writing:
protocol imap {
        mail_plugins = $mail_plugins zlib
}
protocol pop3 {
        mail_plugins = $mail_plugins zlib
}
# Enable these only if you want compression while saving:
plugin {
  zlib_save_level = 6 # 1..9; default is 6
  zlib_save = gz # or bz2, xz or lz4
}' > /etc/dovecot/conf.d/10-websavers-compression.conf

# Restart Dovecot
service dovecot restart

## Convert Existing Emails using process described with the pseudocode here: https://wiki.dovecot.org/Plugins/Zlib
##
## <http://ivaldi.nl/blog/2011/12/06/compressed-mail-in-dovecot/>
##

store=/var/qmail/mailnames/
compress=gzip
#compress=bzip2
maildirlock_bin=/usr/libexec/dovecot/maildirlock

find "$store" -type d -name "cur" | while read maildir;
do
    tmpdir=$(cd "$maildir/../tmp" &>/dev/null && pwd) || exit 1

    find=$(find "$maildir" -type f -name "*,S=*" -mtime +30 ! -name "*,*:2,*,*Z*" -printf "%f\n")

    if [ -z "$find" ];
    then
        continue
    fi

    echo "Before compression:"
    du -b "$maildir"

    echo "$find" | while read filename;
    do
        srcfile="$maildir/$filename"
        tmpfile="$tmpdir/$filename"

        $compress --best --stdout "$srcfile" > "$tmpfile" &&

        # Copy over some things
        chown --reference="$srcfile" "$tmpfile" &&
        chmod --reference="$srcfile" "$tmpfile" &&
        touch --reference="$srcfile" "$tmpfile"
    done

    # Should really check dovecot-uidlist is in $maildir/..
    if lock=$($maildirlock_bin "$maildir/.." 10);
    then
        # The directory is locked now

        echo "$find" | while read filename;
        do
            flags=$(echo $filename | awk -F:2, '{print $2}')

            if echo $flags | grep ',';
            then
                newname=$filename"Z"
            else
                newname=$filename",Z"
            fi

            srcfile=$maildir/$filename
            tmpfile=$tmpdir/$filename
            dstfile=$maildir/$newname

            if [ -f "$srcfile" ] && [ -f "$tmpfile" ];
            then
                #echo "$srcfile -> $dstfile"

                mv "$tmpfile" "$srcfile" &&
                mv "$srcfile" "$dstfile"
            else
                rm -f "$tmpfile"
            fi
        done

        kill -s SIGTERM $lock

        echo "After compression:"
        du -b "$maildir"

        find "$maildir" -type f -name dovecot.index\* -delete
    else
        echo "Failed to lock: $maildir" >&2

        echo "$find" | while read filename;
        do
            rm -f "$tmpdir/$filename"
        done
    fi
done

Changes:

• specify maildirlock_bin var to ensure a different binary location is easy to apply
• Change shebang to bash to ensure the existing kill -s SIGTERM works properly. Running it with sh, it doesn't seem to like SIGTERM on CentOS and therefore leaves the lock in place
• Plesk maildir base (easier for our use)
• Include enabling of zlib support in Dovecot. Also enable automatic storage in gzip compressed format for new messages