Check DKIM signatures of messages stored in a Maildir

dkim-test.sh

#!/bin/sh

MAILDIR="/vmail/example.com/test/Maildir"

DIR_BAD="$MAILDIR/.dkim_bad/new"
DIR_GOOD="$MAILDIR/.dkim_good/new"
DIR_NO_SIG="$MAILDIR/.dkim_no_sig/new"

#-------------------------------

MODE_SORT=

PROGNAME=`basename $0`
PROGDESCR="$PROGNAME - check DKIM signatures of messages stored in a Maildir"

usage () {
    cat >&2 <<EOF

$PROGDESCR

usage: $PROGNAME [-s|-h]

    -s sort messages using predefined directories
    -h brief help
EOF
}

while getopts sh opt; do
    case "$opt" in
        s)
            MODE_SORT=1;;
        # \? - unknown flag
        h|?)
            usage
            [ $opt = "h" ] && exit 0
            exit 1;;
    esac
done


cd $MAILDIR || exit 1

for MSG in ./cur/* ./new/* ; do
    [ -f "$MSG" ] || continue

    RES=`zcat -f "$MSG" | opendkim-testmsg 2>&1`
    printf '.'
    [ $? -ne "0" ] && printf "$MSG\n\n"
    case "$RES" in
        '')
            [ $MODE_SORT ] && mv "$MSG" "$DIR_GOOD/";;
        'opendkim-testmsg: dkim_eom(): Bad signature')
            printf "\nBad signature: $MSG\n"
            [ $MODE_SORT ] && mv "$MSG" "$DIR_BAD/";;
        'opendkim-testmsg: dkim_chunk(): No signature')
            printf "\nNo signature: $MSG\n"
            [ $MODE_SORT ] && mv "$MSG" "$DIR_NO_SIG/";;
        *)
            echo "Unknown test result: $RES";;
    esac
done

echo

Dovecot passwd-file entry:

[email protected]:password::::::userdb_mail=maildir:~/Maildir

main.cf:

sender_bcc_maps = hash:$config_directory/sender_bcc

sender_bcc:

@example.com        [email protected]
@example1.com       [email protected]
@example2.com       [email protected]