STIGQter STIGQter: STIG Summary: Red Hat Enterprise Linux 9 Security Technical Implementation Guide Version: 2 Release: 9 Benchmark Date: 01 Jul 2026:

RHEL 9 must be configured to prevent unrestricted mail relaying.

DISA Rule

SV-257951r1014843_rule

Vulnerability Number

V-257951

Group Title

SRG-OS-000480-GPOS-00227

Rule Version

RHEL-09-252050

Severity

CAT II

CCI(s)

Weight

10

Fix Recommendation

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'

Check Contents

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.

Vulnerability Number

V-257951

Documentable

False

Rule Version

RHEL-09-252050

Severity Override Guidance

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.

Check Content Reference

M

Target Key

5551