[[Open Terminal as root|As '''root''' user]]:
{{Code|<nowikidiv style="border: 1px solid #A3B1BF; padding: .5em 1em; color: #000; background-color: #E6F2FF; margin: 3px 3px 1em 3px;"> SMTP_SERVER=your_isp_smtp_server</nowiki> yum -y install sendmail-cf m4 cd /etc/mail sed -ie "s/.*SMART_HOST.*/define(\`SMART_HOST', \`$SMTP_SERVER')dnl/" sendmail.mc make service sendmail restart}}</div>
Make sure to replace ''your_isp_smtp_server'' on the first line with the hostname or IP address of your ISP SMTP server.