mail not working with IXWebHosting

My hosting company is IXWebHosting and they implemented a new anti-spam system in the beginning of this year. Since then, my WP has stopped sending email notifications to me because of the anti-spam system, and I had to manually change the WP source code to make it work every time I upgraded my WP blog. The strange thing is that I also installed SimpleMachines forum on my IXWebHosting account and never had problem with the email. So does WP use a different way from SimpleMachines to send out emails?

Thanks,