Command line problems with sendmail

I cannot get this shell script to work. The path to sendmail is correct...

#!/bin/bash

echo -e "Subject: email subject\n\nemailbody" | /usr/sbin/sendmail -F fromemail@somedomain.com -t recipientemail@somedomain.com

Depending on your platform, try:

echo -e "Subject: email subject\n\nemailbody" | /usr/sbin/sendmail -f fromemail@somedomain.com recipientemail@somedomain.com