How to: Enable Greylisting to Prevent Spam
==========================================

Greylisting means that the server will initially reject mail from unknown senders and then accept the message upon the 
second attempt. This involves a greet delay, so messages will have to wait a few seconds before being accepted.
Legitimate mail will wait, but spam will generally not. Further information can be found `here <https://www.greylisting.org/>`__.

Enabling both greylisting and tarpitting can be even more effective in reducing spam.
Documentation on how to enable tarpitting can be found :doc:`here </nodeworx/mail_server/spam_and_virus_protection/enable-tarpitting-reduce-spam>`.

.. contents::

To Enable Greylisting
---------------------

#. Log in to the server at the CLI as root, either via SSH or from the terminal
#. At the CLI, use the text editor to open ``/etc/tcprules.d/tcp.smtp``. By default, the contents of the file should look 
   similar to the following:

   .. code-block::

      127.:allow,RELAYCLIENT=""
      ::1:allow,RELAYCLIENT=""
      :allow,LANG="en_US",QMAILQUEUE="/var/qmail/bin/simscan",CHKUSER_MBXQUOTA="99"   

#. Add ``,JGREYLIST=""`` to the end of the first two lines. The ``/etc/tcprules.d/tcp.smtp`` file on 
   some servers will have this information included by default. If that is the case, this step can be skipped

   .. code-block::

      127.:allow,RELAYCLIENT="",JGREYLIST=""
      ::1:allow,RELAYCLIENT="",JGREYLIST=""
      :allow,LANG="en_US",QMAILQUEUE="/var/qmail/bin/simscan",CHKUSER_MBXQUOTA="99"   


#. On the line that begins with ``:allow``, add ``JGREYLIST_DIR="/var/qmail/jgreylist"``

   .. code-block::

      127.:allow,RELAYCLIENT="",JGREYLIST=""
      ::1:allow,RELAYCLIENT="",JGREYLIST=""
      :allow,LANG="en_US",QMAILQUEUE="/var/qmail/bin/simscan",CHKUSER_MBXQUOTA="99",JGREYLIST_DIR="/var/qmail/jgreylist"

#. Save and exit the text editor 
#. At the CLI, use the text editor to open ``/service/smtp/run``. By default, the beginning of the file should look 
   similar to the following: 

   .. code-block::

      #!/bin/sh
      QMAILDUID=`id -u vpopmail`
      NOFILESGID=`id -g vpopmail`
      MAXSMTPD=`cat /var/qmail/control/concurrencyincoming`
      BLACKLIST=`cat /var/qmail/control/blacklists`
      SMTPD="/var/qmail/bin/qmail-smtpd"
      TCP_CDB="/etc/tcprules.d/tcp.smtp.cdb"
      RBLSMTPD="/usr/bin/rblsmtpd"
      HOSTNAME=`hostname`
      VCHKPW="/home/vpopmail/bin/vchkpw"
      #GREYLIST="/var/qmail/bin/jgreylist"
      ARCH=`uname -i`

#. Uncomment the ``GREYLIST`` variable by removing the ``#``

   .. code-block::

      #!/bin/sh
      QMAILDUID=`id -u vpopmail`
      NOFILESGID=`id -g vpopmail`
      MAXSMTPD=`cat /var/qmail/control/concurrencyincoming`
      BLACKLIST=`cat /var/qmail/control/blacklists`
      SMTPD="/var/qmail/bin/qmail-smtpd"
      TCP_CDB="/etc/tcprules.d/tcp.smtp.cdb"
      RBLSMTPD="/usr/bin/rblsmtpd"
      HOSTNAME=`hostname`
      VCHKPW="/home/vpopmail/bin/vchkpw"
      GREYLIST="/var/qmail/bin/jgreylist"
      ARCH=`uname -i`

#. Save and exit the text editor
#. At the CLI, make sure that the ``/var/qmail/jgreylist`` directory is owned by  so that it is owned by ``vpopmail:vchkpw``

   .. code-block::

      [root@server ~]# ls -ld /var/qmail/jgreylist
      drwx------. 2 vpopmail vchkpw 6 May 12  2020 /var/qmail/jgreylist
      [root@server ~]#

   - If the directory is not owned by ``vpopmail:vchkpw``, update the permissions

     .. code-block::

        chown vpopmail:vchkpw /var/qmail/jgreylist     

#. Restart smtp

   .. code-block::

      service smtp restart