This is postfix autoresponder is originally written by Charles Hamilton, rewritten by asmpro and now rewritten by me for my purpose.

Installation

Create autoresponder user

useradd -d /var/spool/autoresponder -s $(which nologin) autoresponder

Compile autoresponder

go get git.gurkengewuerz.de/Gurkengewuerz/go-autoresponder

Copy autoresponder binary to /usr/local/sbin

cp ~/gowork/bin/autoresponder /usr/local/sbin/
chown autoresponder:autoresponder /usr/local/sbin/autoresponder
chmod 6755 /usr/local/sbin/autoresponder

Create response_dir

mkdir -p/var/spool/autoresponder/responses
chown -R autoresponder:autoresponder /var/spool/autoresponder
chmod -R 0770 /var/spool/autoresponder

Edit /etc/postfix/master.cf

Replace line:

smtp inet n - - - - smtpd

with these two lines (second must begin with at least one space or tab):

smtp inet n - - - - smtpd
  -o content_filter=autoresponder:dummy

At the end of file append the following two lines:

autoresponder unix - n n - - pipe
  flags=Fq user=autoresponder argv=/usr/local/sbin/autoresponder -s ${sender} -r ${recipient} -c <REPLACE WITH CONFIG PATH> -logfile <PATH TO LOG>

Set additional postfix parameter

postconf -e 'autoresponder_destination_recipient_limit = 1'

Restart postfix

service postfix restart