Ajax form issue with email provider

Ajax form issue with email provider

I would be forever grateful if someone could help me out.
I have an Ajax/PHP Contact Form on my site - my email address along with
the site is hosted with Dreamhost. Here is the issue - anytime someone
fills out the contact form, more importantly the part where it asks for
their email address: if their email address ends with @gmail.com
@hotmail.com @live.com (and there only the ones i've tested) i never get
the email..but if they put any other email address it comes through no
problem?
I've checked the form code and everything seems fine - i'm starting to
think it's a dreamhost server issue but have no idea where to go from
here.
Any insight would be greatly appreciated.