postfix_transport_redirect_mail.bash

#!/bin/bash

TO="user@example.com"
FROM="user@example.com"
SUBJECT="Invalid sending domain on `hostname`"
MESSAGE="The attached mail did not comply with our sender domains on `hostname`."

TMPFILE=$(mktemp)
trap "rm -f $TMPFILE" 0 1 2 3 15

HEADER="To: $TO
From: $FROM
Subject: $SUBJECT
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Content-Type: multipart/mixed; boundary=\"_----------=_148120056728766463\"

This is a multi-part message in MIME format.

--_----------=_148120056728766463
Content-Transfer-Encoding: 7bit
Content-Type: text/plain; charset=\"utf-8\"

$MESSAGE

--_----------=_148120056728766463
Content-Disposition: attachment; filename=\"attached.eml\"
Content-Type: message/rfc822; name=\"attached.eml\"
Content-Transfer-Encoding: 8bit
"

FOOTER="
--_----------=_148120056728766463--
"

echo -e "$HEADER" >> $TMPFILE
#cat | base64 -w 60 >> $TMPFILE
cat >> $TMPFILE
echo -e "$FOOTER" >> $TMPFILE

#cat $TMPFILE
/usr/sbin/sendmail -t -f $FROM -F "" < $TMPFILE

exit $?