Disable offsite mail relaying

Question

RHEL6 | High Sev

Vulnerability Title SMTP unauthenticated 3rd-party mail relay

Vuln Description lity is that other organizations, in an attempt to stop the flow of spam, may throw away any mail originating from your server (including legitimate mail from your users).

Answer 1

Following FIX Helped, take backup of file

1. Comment out the below entry cd /etc/mail

[root@mail]# cat sendmail.mc | grep -v ^dnl | grep -i smart define(SMART_HOST',relaymail.sapient.com')dnl [root@mail]# [root@mail]#

2. Below entry should be commented out [root@ mail]# cat sendmail.mc | grep -v ^dnl | grep -i mailerta FEATURE(mailertable',hash -o /etc/mail/mailertable.db')dnl

[root@mail]# cp -p sendmail.mc sendmail.mc.bkp.date +%F [root@mail]#

[root@mail]# m4 sendmail.mc > sendmail.cf

3. Add below entry in /etc/mail/mailertable to disable offsite mail relay

gmail.com smtp:[192.168.100.x] . error:Mail to external domain is prohibited [root@ mail]#

it helped to fix. Hopefully will help, i searched a lot and finally this worked so thought to share.