Exim append text to message body for certain attachment extensions

Question

I've already disabled email delivery to our servers if certain attachment extension found. But some extension I just can't disable, because our customers are frequently using them, like .zip

How can I configure exim to just prepend some text into the message body if certain attachment extension found?

Answer 1

Can you do that using transport_filter on your smtp driver

http://www.exim.org/exim-html-3.20/doc/html/spec_14.html#SEC417

remote_smtp:
  driver = smtp
  transport_filter  = /bin/sh -c "/etc/exim/extras/footer.sh ${message_id}"

Example:

[root@web ~]# /bin/cat << EOF > /etc/exim/extras/footer.sh
#!/bin/sh

BODY=`/usr/sbin/exim -Mvb $1`

if [[ $BODY == *".zip"* ]]; then
    /usr/bin/altermime --multipart-insert --force-into-b64 --disclaimer-html=/etc/exim/extras/has-zip.html --input=/tmp/altermime.$DATE --force-for-bad-html
else
    /usr/bin/altermime --multipart-insert --force-into-b64 --disclaimer-html=/etc/exim/extras/empty.html --input=/tmp/altermime.$DATE --force-for-bad-html
fi

/bin/cat /tmp/altermime.$DATE
/bin/rm /tmp/altermime.$DATE

exit
EOF

File dependency.

[root@web ~]# /bin/cat << EOF > /etc/exim/extras/has-zip.html
This message contains .ZIP file.
EOF

File dependency.

[root@web ~]# /bin/echo "" > /etc/exim/extras/empty.html