Localhost SMPT w/ password

I managed to setup SMPT (using postfix enabler) on my laptop to get around my university blocking outside IP addresses from sending mail through them.

However I cannot figure out how to get password protection to stop others from abusing my SMTP. Does anyone know how I would go about setting up a password or blocking everyone except myself?

By default postfix only lets through smtp requests from localhost, so you should'nt have anything to worry about.