Formmail Authentication not Working

I set up formmail per inmotionhostinsg's instructions and I can't get it to work because it is requiring authentication and can't get the authentication to work. This is the message that I am getting (minus personal info): Application Error An error has occurred in the program SMTP command [RCPT TO:] gave response [550 SMTP AUTH is required for message submission on port 587 ] at (eval 8) line 179, line 6.