[ubuntu] Request Tracker email out. Postfix or SSMTP not working.

So I'm trying to configure Request Tracker 4. RT doesn't need to recieve emails, as yet, but I'd like to configure it to send emails to collegues tho whom I assign tickets.

Our email is handled outside of our company. I have tried to configure RT to use Postfix to send emails through our 'smarthost' but but /var/log/mail.log tells me "unkown user:"

OS is Ubuntu 12.10.

the following is how I set up postfix:
dpkg-reconfigure postfix
tar cfz /var/backups/etc-postfix_20130526.tgz /etc/postfix/
echo "mail.mycompany.com rtfour@mycompany.com:RT4Password" >>/etc/postfix/sasl_passwd
chmod 600 /etc/postfix/sasl_passwd
chown root:root /etc/postfix/sasl_passwd
postmap /etc/postfix/sasl_passwd
postconf -e "relayhost = [mail.mycompany]:587"
postconf -e "smtp_sasl_auth_enable = yes"
postconf -e "smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd"
postconf -e "smtp_sasl_security_options = "
postconf -e "smtp_use_tls = yes"
postfix check
postfix reload

that sends no email and tells me "unkown user:"

None of the online help seems to add anything for basic configuration. So I thought perhaps I could use ssmtp as I did with my nagios host. Unfotunately, while nagios was easy to get sending via ssmtp. RT still doesn't work. ssmtp is woking now. I can send mail from the cli.

What would I need to do to get RT to send email via ssmtp? Or what do I need to fix to get postfix to work?