Tip: Add Disclaimer To Only Outgoing Email Using Altermime
On our mail server at work, we added a disclaimer to all outgoing emails using Altermime. This has been working fine for a few months now. There was just one thing that annoyed me about it, it added to all outgoing emails, including internal mail between users.
So I went about trying to find a solution and eventually found out how to do it so thought I’d share it here and also keep it as a reference to me as it took me ages to find it 
# tar -xzvf altermime-0.2.2.tar.gz
# cd altermime-0.2.2
# make
# cp altermime /usr/bin/
# chown root.root /usr/bin/altermime
# chmod 755 /usr/bin/altermime
# mkdir /var/spool/filter
# chown filter.filter /var/spool/filter
# chmod 750 /var/spool/filter # Creating The Script To Run alterMIME
# vi /etc/postfix/disclaimer
#!/bin/sh
# Localize these.
INSPECT_DIR=/var/spool/filter
SENDMAIL=/usr/sbin/sendmail
#Exit codes from
EX_TEMPFAIL=75
EX_UNAVAILABLE=69
RECIP=`echo $* | awk '{print $NF}'| tr [A-Z] [a-z]`
SENDER=`echo $* | awk '{print $2}'| tr [A-Z] [a-z]`
RECIP_DOMAIN=`echo $RECIP | awk -F"@" '{print $2}'`
SEND_DOMAIN=`echo $SENDER | awk -F"@" '{print $2}'`
# Clean up when done or when aborting.
trap "rm -f in.$$" 0 1 2 3 15
# Start processing.
cd $INSPECT_DIR || { echo $INSPECT_DIR does not exist; exit $EX_TEMPFAIL; }
cat >in.$$ || { echo Cannot save mail to file; exit $EX_TEMPFAIL; }
if [ $RECIP_DOMAIN == $SEND_DOMAIN ]; then
DISCLAIMER=/etc/postfix/empty_disclaimer.txt
else
DISCLAIMER=/etc/postfix/disclaimer.txt
fi
/usr/bin/altermime --input=in.$$
--disclaimer=$DISCLAIMER
--disclaimer-html=$DISCLAIMER ||
{ echo Message content rejected; exit $EX_UNAVAILABLE; }
$SENDMAIL "$@"
# chgrp filter /etc/postfix/disclaimer
# chmod 750 /etc/postfix/disclaimer
/etc/postfix/empty_disclaimer.txt is the disclaimer which will get used for internal email, ie when the sending domain is the same as the receiving domain, in my case I made it a blank file.
/etc/postfix/disclaimer.txt is the disclaimer which gets added to all other emails, in that we have some stuff saying it may be copyrighted or something, can’t remember now.
# vi /etc/postfix/disclaimer.txt
# vi /etc/postfix/empty_disclaimer.txt
Edit master.cf :
# vi /etc/postfix/master.cf
127.0.0.1:smtp inet n - y - - smtpd
smtp inet n - y - - smtpd
-o content_filter=dfilt:
dfilt unix - n n - - pipe
flags=Rq user=filter argv=/etc/postfix/disclaimer -f ${sender} — ${recipient}
# Restart Postfix
# postfix reload
