The most efficient way to send emails from Ubuntu shell script or cron

What is the most efficient way to send an email from Ubuntu shell script or cron? I have found sendEmail wins the battle:

sudo apt-get install sendemail
echo $CONTENT_BODY | \
sendEmail -f $FROM -t $TO1 $TO2 \
-s $MAIL_SERVER_HOSTNAME -u $SUBJECT > /dev/null 

Here is an example of its usage from cron BTW.