The following script/code will send out a formatted email using sSMTP (or sendmail):
#!/bin/bash
CURDATE=`date`
sendmail -oi user@domain.com << EOF
From: Your User <user2@domain2.com>
To: user@domain.com
Subject: SERVER INFO: Booted on $CURDATE
The server has just been booted on $CURDATE.
EOF