|Securing and Optimizing Linux: RedHat Edition -A Hands on Guide|
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Now that our macro configuration file sendmail.mc is created, we can build the sendmail configuration file sendmail.cf from these statements with the following commands:
[root@deep] /# cd /var/tmp/sendmail-version/cf/cf/ [root@deep ]/cf# m4 ../m4/cf.m4 sendmail.mc > /etc/mail/sendmail.cf
: Here, the ../m4/cf.m4 tells m4 program where to look for its default configuration file information.
Since our local clients machines never receive mail directly from the outside world, and relay, send all their mail through the Mail Hub server, we will create a special file called null.mc which, when later processed, will create a customized sendmail.cf configuration file that responds to this special setup for our neighbour or local server client machines. This m4 macro file is simple to create and configure because it doesn't need a lot of features, as the configuration file -sendmail.mc, for the Central Mail Hub server did.
The null.mc file is for the local or neighbour client and server machines only
Create the null.mc file, touch /var/tmp/sendmail-version/cf/cf/null.mc and add the following lines:
: We advice that with this kind of configuration, no mailers should be defined, and no aliasing or forwarding is done.
Now that our macro configuration file null.mc is created, we can build the Sendmail configuration file sendmail.cf from these statements in all our neighbor servers, and client machines with the following commands:
[root@deep] /# cd /var/tmp/sendmail-version/cf/cf/ [root@deep ]/cf# m4 ../m4/cf.m4 null.mc > /etc/mail/sendmail.cf
No mail should ever again be delivered to your local machine. Since there will be no incoming mail connections, you no longer needed to run a Sendmail daemon on your neighbor or local server, client machines. To stop the Sendmail daemon from running on your neighbor or local server, or client machines, edit or create the /etc/sysconfig/sendmail file and change/add the lines that read:
DAEMON=yes To read: DAEMON=no And: QUEUE=1h
: The QUEUE=1h under /etc/sysconfig/sendmail file causes Sendmail to process the queue once every 1 hour. We leave that line in place because Sendmail still needs to process the queue periodically in case the Mail Hub is down.
Remove the following files from your system, use the following command:
[root@client /]# rm -f /usr/bin/newaliases [root@client /]# rm -f /usr/man/man1/newaliases.1 [root@client /]# rm -f /usr/man/man5/aliases.5
: Local machines never use aliases, access, or other maps database. Since all map file databases are located and used on the Central Mail Hub Server for all local machines we may have on the network, we can safety remove the following commands and man pages from all our local machines.
Remove the unnecessary Procmail program from your entire local Sendmail server or client. Since local machines send all internal and outgoing mail to the mail Hub Server for future delivery, we don't need to use a complex local delivery agent program like Procmail to do the job. Instead we can use the default /bin/mail program. To remove Procmail from your system, use the following command:
[root@client ]# rpm -e procmail