Cannot forward email to Sprint phone

I want to forward email from my email box to a Sprint phone.

The Sprint phone can receive an email if I email it directly.

The Outlook email rule forwards email perfectly to an email address, so that part is working - however, if you put in the Sprint email address, it will NOT receive those forwarded emails.

The problem appears to be that the Sprint System is not allowing forwarded emails to go through to the phone. I'm wondering if Sprint has some type of filtering system.

Anyone have any experience with this?