AlmaLinux OS 9 must be configured to prevent unrestricted mail relaying.
Overview
| Finding ID | Version | Rule ID | IA Controls | Severity |
| V-269252 | ALMA-09-019490 | SV-269252r1050134_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 |
| CloudLinux AlmaLinux OS 9 Security Technical Implementation Guide | 2025-05-22 |
Details
| Check Text (C-73283r1049387_chk) |
| Note: If postfix is not installed, this is Not Applicable. Verify AlmaLinux OS 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-73184r1048133_fix) |
| Modify the postfix configuration file to restrict client connections to the local network with the following command: $ postconf -e 'smtpd_client_restrictions = permit_mynetworks,reject' |