<div style="border: 1px solid #A3B1BF; padding: .5em 1em; color: #000; background-color: #E6F2FF; margin: 3px 3px 1em 3px;">
SMTP_SERVER=your_isp_smtp_server
yum -y install sendmail-cf sed -ie "s/.*SMART_HOST.*/define(\`SMART_HOST', \`$SMTP_SERVER')dnl/" /etc/mail/sendmail.mcm4
cd /etc/mail
makesed -ie "s/.*SMART_HOST.*/define(\`SMART_HOST', \`$SMTP_SERVER')dnl/" sendmail.mc m4 sendmail.mc > sendmail.cf
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.
If you need to provide a username and password to use the SMTP server, you'll need to do this too:
<div style="border: 1px solid #A3B1BF; padding: .5em 1em; color: #000; background-color: #E6F2FF; margin: 3px 3px 1em 3px;">
SMTP_SERVER=your_isp_smtp_server
USERNAME=your_smtp_username
PASSWORD=your_smtp_password
cd /etc/mail
echo "AuthInfo:$SMTP_SERVER \"U:$USERNAME\" \"P:$PASSWORD\" \"M:PLAIN\"" >> access
m4 sendmail.mc > sendmail.cf
makemap hash access < access
</div>