I seem to have a similar problem to this guy:
http://www.silverstripe.org/archive/show/154824#post154824
I have 2 forms set on a site I setup, one is a contact form and the other is a resume submit/job app form. For both of the form I have set 2 Email Recipients to be notified when a submission has been made. It would seem that I am getting the emails but the other person is not. I'm using gmail to retrieve my work email for the form to be sent to, and the other person is using outlook I believe. Any Ideas on why one person might not be getting it?