Chapter 22. Configuring Postfix MTA by using RHEL system roles

Procedure

1. Create a playbook file, for example ~/playbook.yml, with the following content:

   ---
   - name: Manage Postfix
     hosts: managed-node-01.example.com
     tasks:
       - name: Install postfix
         ansible.builtin.package:
           name: postfix
           state: present
   
       - name: Configure null client for only sending outgoing emails
         ansible.builtin.include_role:
           name: rhel-system-roles.postfix
         vars:
           postfix_conf:
             myhostname: server.example.com
             myorigin: "$mydomain"
             relayhost: smtp.example.com
             inet_interfaces: loopback-only
             mydestination: ""
             relay_domains: "{{ lookup('ansible.builtin.pipe', 'postconf -h default_database_type') }}:/etc/postfix/relay_domains"
           postfix_files:
             - name: relay_domains
               postmap: true
               content: |
                 example.com OK
                 example.net OK

   The settings specified in the example playbook include the following:

   myhostname: <server.example.com>

   The internet hostname of this mail system. Defaults to the fully-qualified domain name (FQDN).

   myorigin: $mydomain

   The domain name that locally-posted mail appears to come from and that locally posted mail is delivered to. Defaults to $myhostname.

   relayhost: <smtp.example.com>

   The next-hop destination(s) for non-local mail, overrides non-local domains in recipient addresses. Defaults to an empty field.

   inet_interfaces: loopback-only

   Defines which network interfaces the Postfix server listens on for incoming email connections. It controls whether and how the Postfix server accepts email from the network.

   mydestination

   Defines which domains and hostnames are considered local.

   relay_domains: "hash:/etc/postfix/relay_domains"

   Specifies the domains that Postfix can forward emails to when it is acting as a relay server (SMTP relay). In this case the domains will be generated by the postfix_files variable. On RHEL 10, you have to use relay_domains: "lmdb:/etc/postfix/relay_domains".

   postfix_files

   Defines a list of files that will be placed in the /etc/postfix/ directory. Those files can be converted into Postfix Lookup Tables if needed. In this case postfix_files generates domain names for the SMTP relay.

   For details about the role variables and the Postfix configuration parameters used in the playbook, see the /usr/share/ansible/roles/rhel-system-roles.postfix/README.md file and the postconf(5) manual page on the control node.

2. Validate the playbook syntax:

   $ ansible-playbook --syntax-check ~/playbook.yml

   Note that this command only validates the syntax and does not protect against a wrong but valid configuration.

3. Run the playbook:

   $ ansible-playbook ~/playbook.yml