RHEL 9 must be configured to prevent unrestricted mail relaying.
Severity | Group ID | Group Title | Version | Rule ID | Date | STIG Version |
|---|---|---|---|---|---|---|
| medium | V-257951 | SRG-OS-000480-GPOS-00227 | RHEL-09-252050 | SV-257951r1014843_rule | 2025-02-27 | 2 |
| 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. |
| ℹ️ Check |
|---|
| 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 |
|---|
| 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' |