I have used this sometime, which was taken from some tutorial example, and it works great for me.
(
echo "From:
me@my_company.com"
echo "To:
you@your_company.com"
echo "MIME-Version: 1.0"
echo "Content-Type: multipart/mixed;"
echo ' boundary="PAA08673.1018277622/server.domain.com"'
echo "Subject: Test Message"
echo ""
echo "This is a MIME-encapsulated message"
echo ""
echo "--PAA08673.1018277622/server.domain.com"
echo "Content-Type: text/html"
echo ""
echo "<HTML>
<BODY bgcolor=blue>
<blockquote><font color=red>Test</font> <font color=white>Message</font> <font color=blue>Body</font></blockquote>
</body>
</html>"
echo "--PAA08673.1018277622/server.domain.com"
) | sendmail -t
