The Red Hat Enterprise Linux operating system must be configured to prevent unrestricted mail relaying.

From Red Hat Enterprise Linux 7 Security Technical Implementation Guide

Associated with: CCI-000366

SV-86921r3_rule The Red Hat Enterprise Linux operating system must be configured to prevent unrestricted mail relaying.

Vulnerability discussion

If unrestricted mail relaying is permitted, unauthorized senders could use this host as a mail relay for the purpose of sending spam or other unauthorized activity.

Check content

Verify the system is configured to prevent unrestricted mail relaying. Determine if "postfix" is installed with the following commands: # yum list installed postfix postfix-2.6.6-6.el7.x86_64.rpm If postfix is not installed, this is Not Applicable. If postfix is installed, determine if it is configured to reject connections from unknown or untrusted networks with the following command: # postconf -n smtpd_client_restrictions smtpd_client_restrictions = permit_mynetworks, reject If the "smtpd_client_restrictions" parameter contains any entries other than "permit_mynetworks" and "reject", this is a finding.

Fix text

If "postfix" is installed, modify the "/etc/postfix/main.cf" file to restrict client connections to the local network with the following command: # postconf -e 'smtpd_client_restrictions = permit_mynetworks,reject'

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