Common Controls Hub
OL 8 must be configured to prevent unrestricted mail relaying.
If unrestricted mail relaying is permitted, unauthorized senders could use this host as a mail relay to send spam or for other unauthorized activity.
Oracle Linux 8 Security Technical Implementation Guide
Check Text ( C-52329r780249_chk )
Verify the system is configured to prevent unrestricted mail relaying.
Determine if "postfix" is installed with the following commands:
$ sudo yum list installed postfix
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:
$ sudo 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 (F-52283r780250_fix)
If "postfix" is installed, modify the "/etc/postfix/main.cf" file to restrict client connections to the local network with the following command:
$ sudo postconf -e 'smtpd_client_restrictions = permit_mynetworks,reject'