How to add a Disclaimer To Outgoing Emails in Postfix

We have already dicussed how to install and configure postfix now we will learn about How to add a Disclaimer To Outgoing Emails in Postfix using altermime.

alterMIME is a small program which is used to alter your mime-encoded mailpacks as typically received by Inflex, Xamime and AMaViS.

What can alterMIME do?

Insert disclaimers
Insert arbitary X-headers
Modify existing headers
Remove attachments based on filename or content-type
Replace attachments based on filename

Installing alterMIME in debian

Use the following command to install altermime

#aptitude install altermime

This will complete the installation.

Configure altermime

Next we need to create the user filter with the home directory /var/spool/filter filter - alterMIME will be run as that user

#useradd -r -c “Postfix Filters” -d /var/spool/filter filter

#mkdir /var/spool/filter

#chown filter:filter /var/spool/filter

#chmod 750 /var/spool/filter

Afterwards we create the script /etc/postfix/disclaimer which executes alterMIME. Debian’s alterMIME package comes with a sample script that we can simply copy to /etc/postfix/disclaimer

#cp /usr/share/doc/altermime/examples/postfix_filter.sh /etc/postfix/disclaimer

#chgrp filter /etc/postfix/disclaimer

#chmod 750 /etc/postfix/disclaimer

Now we need to add disclaimer to only outgoing email

we create the file /etc/postfix/disclaimer_emails which holds all sender email addresses (one per line) for which alterMIME should add a disclaimer

#vi /etc/postfix/disclaimer_emails

admin@domain.com
user1@domain.org

Save and exit the file

Now we open /etc/postfix/disclaimer and modify some configuration you can check this file

Next we need the text file /etc/postfix/disclaimer.txt which holds our disclaimer text. Debian’s alterMIME package comes with a sample text that we can use for now

#cp /usr/share/doc/altermime/examples/disclaimer.txt /etc/postfix/disclaimer.txt

Finally we have to tell Postfix that it should use the /etc/postfix/disclaimer script to add disclaimers to outgoing emails. Open /etc/postfix/master.cf and add -o content_filter=dfilt: to the smtp line:

#vi /etc/postfix/master.cf

# # Postfix master process configuration file. For details on the format # of the file, see the master(5) manual page (command: “man 5 master”). # # ========================================================================== # service type private unpriv chroot wakeup maxproc command + args # (yes) (yes) (yes) (never) (100) # ==========================================================================

smtp inet n - - - - smtpd

-o content_filter=dfilt: [...]
at the end of the file add the following lines

[...]
dfilt unix - n n - - pipe
flags=Rq user=filter argv=/etc/postfix/disclaimer -f ${sender} -- ${recipient}

Save and exit the file.

Now you need to restart the postfix mail server using the following command

#/etc/init.d/postfix restart