Vulnerability Discussion

If unrestricted mail relaying is permitted, unauthorized senders could use this host as a mail relay to send spam or for other unauthorized activity.

Check

Note: If postfix is not installed, this is not applicable.

Verify RHEL 10 is configured to prevent unrestricted mail relaying 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", and the additional entries have not been documented with the information system security officer, this is a finding.

Fix

Configure RHEL 10 so that the postfix configuration file restricts client connections to the local network with the following command:

$ sudo postconf -e 'smtpd_client_restrictions = permit_mynetworks,reject'