Mail is generated internally by the Postfix system itself, in order to notify the postmaster of a problem (this path is also indicated with the unlabeled arrow).The Postfix system can be configured to notify the postmaster of SMTP protocol problems, UCE policy violations, and so on.
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This article provides an introduction to Mail Transfer Agent (MTA) configuration on Linux, with specific reference to the information needed for the RHCE EX300 certification exam.
Remember, the exams are hands-on, so it doesn't matter which method you use to achieve the result, so long as the end product is correct.
Installation
The Postfix service is installed from a Yum repository using the following command.
Turn on the Postfix service and make sure it starts automatically on reboot.
The Postfix service is configured using the '/etc/postfix/main.cf' file. Configuration changes have to be followed by a restart of the service.
Firewall
The server acting as a mail transfer agent must have the TCP port 123 open. This can be achieved by adding the following entry to the type of firewall script described here.
![Postfix configuration mail Postfix configuration mail](/uploads/1/2/6/3/126360896/744084995.png)
SELinux
If you are using SELinux, you will need to consider the following points.
The SELinux booleans associated with the Postfix service are displayed using the
getsebool
command.The
setsebool
command is used to set a specific boolean value.More information on SELinux can be found here.
Configure a mail transfer agent (MTA) to accept inbound email from other systems
To allow Postfix to accept inbound email, edit the ' /etc/postfix/main.cf' file, setting the following values relevant for your network.
Remember to restart or reload the service for the changes to take effect.
Test the service is accessible from another machine using telnet on port 25.
You may need to install telnet to perform this test. This is done using the following command.
Configure an MTA to forward (relay) email through a smart host
To allow Postfix to accept relay email, edit the ' /etc/postfix/main.cf' file, setting the following value to the relevant host.
Remember to restart or reload the service for the changes to take effect.
Test the change by sending an email.
Security
![Postfix Configuration File Pleskova Postfix Configuration File Pleskova](/uploads/1/2/6/3/126360896/119157503.png)
Host level security is provided by the Linux firewall, as described previously.
For more information see:
Hope this helps. Regards Tim...