RHEL 9 must be configured to prevent unrestricted mail relaying.
Overview
| Finding ID | Version | Rule ID | IA Controls | Severity |
| V-257951 | RHEL-09-252050 | SV-257951r1014843_rule | Medium |
| Description |
| 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. |
| STIG | Date |
| Red Hat Enterprise Linux 9 Security Technical Implementation Guide | 2024-12-04 |
Details
| Check Text (C-61692r1014842_chk) |
| If postfix is not installed, this is Not Applicable. Verify RHEL 9 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 (ISSO), this is a finding. |
| Fix Text (F-61616r925839_fix) |
| Modify the postfix configuration file to restrict client connections to the local network with the following command: $ sudo postconf -e 'smtpd_client_restrictions = permit_mynetworks,reject' |