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 | CCI-000366 | 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-269252r1050134_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'