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Network Services—Internet ServersIf you are not running a complicated mail server, you may stick with the defaultsendmail for your daily mail transfer use.We will also look into Postfix (which is also another widely used and a slightly moreadvanced MTA), later in this chapter.SendmailChances are that the default sendmail from the base system is the latest and the moststable sendmail distribution for your current installation. However, the sendmail inthe base system is not updated frequently. Hence, if you feel that you may want touse a newer version of the sendmail for any reason, you can find the latest version inthe ports under the /usr/ports/mail/sendmail directory.The sendmail program can operate in various modes—from a fully loaded MTA thataccepts mail from other hosts and routes mails to their destinations, to a minimalconfiguration that lets local mails be submitted.To completely enable sendmail, you can use the following lines in the/etc/rc.conf file:sendmail_enable="YES"And then start the sendmail by calling its rc script as shown here:# /etc/rc.d/sendmail startThis will start the sendmail process that listens on all active network interfaces onTCP port 25, for incoming SMTP requests.If you do not want to enable sendmail to receive incoming emails over the network,you can modify the rc.conf file as shown here:sendmail_enable="NO"Note that this will not actually disable the sendmail. After restarting the process, youwill find the sendmail process still running and listening only for SMTP traffic (TCPport 25) on the loopback interface (127.0.0.1). So it will not be able to actually receiveemails over the network, and only accepts SMTP connection from the localhost onthe loopback interface, and routes the local mail to their destination.If you want to completely disable sendmail, you should modify the rc.conf file asshown here:senmail_enable="NONE"[ 224 ]