The most important thing is if the email is being sent from a dreamhost webserver that the FROM address be on that same domain. (i.e. webmaster@your_domain.com)
What specifically will not work, is the FROM address being the users address that they are submitting via the form.
The other thing that works best is if you are only emailing TO an account at dreamhost.
Another thing that works best when it can’t be mailed TO your own account is to use SMTP.