Send mail from OS X without email account On linux, I use exim4 to send mail to a public email address. I don't have to authenticate or anything. It pretends its noreply@example.com and sends it to someone@example.com.  Is it possible to do the same on OS X?

I have a cron job, and I want to send mail from the root user as noreply@example.com like with my linux box. I looked up postfix configuration as it seems to be the method used, but all the examples require authentication. Is there anyway to avoid this?
Yes, there's no problem in sending emails like that from OS X. 

First, you'll need to configure postfix to relay emails. Once you've done that, you'll need to create the script that sends the email. I'm not sure what method you're using to send email on the Linux system, but something very similar should work on OS X, for example, using mailx.

Assuming that your upstream mail provider (the system your OS X system is relaying mail through, ie the mail relay) doesn't require authentication, you won't need to configure mail authentication.