BaselineWatch
Desk
Your fleet and your work Fleetyour releases and the hardware they run onTriagewhat needs a decisionWatchlistthe products and platforms you runSaved searchesthe lists you come back to
This instance Sourceswhat is read, how often, under what termsDigestthe daily or weekly summary, and alerts
How it is drawn Appearancethe look and the colour schemeBrandingthe mark this instance wears
Owner sign-in

RHEL-09-252050 RHEL 9 must be configured to prevent unrestricted mail relaying.

DISA STIG library V2R10
All changes in this version
first version loaded CAT II

Maps to CM-6 via CCI-000366

Title

RHEL 9 must be configured to prevent unrestricted mail relaying.

Control

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.

Discussion

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.

Related controls

CCI-000366

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'