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Red Hat Enterprise Linux Server release 6.3 (Santiago)
The current version of RHEL 6 is RHEL 6.8. 6.3 is several years old and some very important vulnerabilities have been fixed since then, most notably one named Shellshock.
I am confused how mails are getting delivered since SMARTHOST is not configured . Any pointers ?
A smarthost tells the mail server not to attempt to figure out how to deliver mail, i.e. look up MX records and deliver mail, but rather to blindly send all outgoing mail to a specific host known as a smarthost which will then be responsible for doing the MX lookup and delivering the mail.
Think of it this way ... you have one server that is allowed to initiate connections out of your company on 25/tcp called outgoing.example.com and you have web00.example.com - web19.example.com and app00.example.com - app19.example.com. All of these 4 web and app servers need to send mail to external customers, but they can't do so directly due to firewall restrictions, so you set them all to use a smarthost (known as a relayhost in Postfix) of outgoing.example.com. Then when any of those 40 servers needs to send an email to a yahoo.com (or any other external) address, it doesn't look up the address, it blindly sends it to outgoing.example.com at which point outgoing.example.com does an MX lookup for the mail servers that handle yahoo.com email and sends the message to the Yahoo mail server with the lowest priority.
Does that make sense? Hope this helps. Barry -- redhat-sysadmin-list mailing list [email protected] https://www.redhat.com/mailman/listinfo/redhat-sysadmin-list
