Dell PowerProtect Cyber Recovery 19.16 Product Guide

Configuring the Postfix email service

Postfix is an open-source mail transfer agent that is included with most non-Windows systems.

1. If your system has an active firewall, ensure that port 25 is open on the firewall. If necessary, open port 25 on the firewall:

   # iptables -I INPUT -p tcp --dport 25 -j ACCEPT

2. Open /etc/postfix/main.cf in an editor, and modify it as shown in the following examples:
   1. Add the inet address of the virtual Ethernet adapter or network interface card (NIC) that is used for SMTP communication:

      # RECEIVING MAIL
      #
      # Note: you need to stop/start Postfix when this parameter changes.
      #
       inet_interfaces = all
      #inet_interfaces = $myhostname
      #inet_interfaces = $myhostname, localhost
      #inet_interfaces = localhost
      

      NOTE:Ensure that you do not uncomment more than one inet_interface.
   2. Add the fully qualified domain name (FDQN) of the host running the Postfix service:

      # INTERNET HOST AND DOMAIN NAMES
      #
      # The myhostname parameter specifies the internet hostname of this
      # mail system. The default is to use the fully-qualified domain name
      # from gethostname(). $myhostname is used as a default value for many
      # other configuration parameters.
      # 
      myhostname = <FDQN of the host running the Postfix service> 

   3. Add the mail server name:

      # INTERNET OR INTRANET
      # 
      # The relayhost parameter specifies the default host to send mail to 
      # when no entry is matched in the optional transport (5) table. When 
      # no relayhost is given, mail is routed directly to the destination.
      #
      # On an intranet, specify the organizational domain name. If your
      # internal DNS uses no MX records, specify the name of the intranet
      # gateway host instead.
      #
      # In the case of SMTP, specify a domain, host, host:port, [host]:port,
      # [address] or [address]:port; the form [host] turns off MX lookups.
      # If you're connected via UUCP, see also the deafult_transport parameter.
      #
       relayhost = <mail server name>
      #

   4. If you receive a Relay Access denied message when sending email messages, check the mynetworks property and set it appropriately:

      # TRUST AND RELAY CONTROL
      
      # The mynetworks parameter specifies the list of "trusted" SMTP
      # clients that have more privileges than "strangers".
      #
      # In particular, "trusted" SMTP clients are allowed to relay mail
      # through Postfix.  See the smtpd_recipient_restrictions parameter
      # in postconf(5).
      #
      # You can specify the list of "trusted" network addresses by hand
      # or you can let Postfix do it for you (which is the default).
      #
      # By default (mynetworks_style = subnet), Postfix "trusts" SMTP
      # clients in the same IP subnetworks as the local machine.
      # On Linux, this works correctly only with interfaces specified
      # with the "ifconfig" command.
      #
      # Specify "mynetworks_style = class" when Postfix should "trust" SMTP
      # clients in the same IP class A/B/C networks as the local machine.
      # Don't do this with a dialup site - it would cause Postfix to "trust"
      # your entire provider's network.  Instead, specify an explicit
      # mynetworks list by hand, as described below.
      #
      # Specify "mynetworks_style = host" when Postfix should "trust"
      # only the local machine.
      #
      # mynetworks_style = class
      # mynetworks_style = subnet
      # mynetworks_style = host
      # Alternatively, you can specify the mynetworks list by hand, in
      # which case Postfix ignores the mynetworks_style setting.
      #
      # Specify an explicit list of network/netmask patterns, where the
      # mask specifies the number of bits in the network part of a host
      # address.
      #
      # You can also specify the absolute pathname of a pattern file instead
      # of listing the patterns here. Specify type:table for table-based lookups
      # (the value on the table right-hand side is not used).
      #
        mynetworks = 168.100.189.0/28, 127.0.0.0/8
      # mynetworks = $config_directory/mynetworks
      # mynetworks = hash:/etc/postfix/network_table

3. Reload the Postfix configuration file.

   # postfix reload

4. Stop and start Postfix:

   # postfix stop
   # postfix start

5. Optionally, check the Postfix status:

   # postfix status