Suppliers do not get emails from iSupplier

 Hi Guys, I was wondering if anyone can help us.  We set up iSupplier with one supplier and everything works great except that the supplier does not get emails from our server everytime we make changes on PO or new PO.  They need to log into the iSupplier website every few hours to check new PO or changes.  They do get notifications though once they logged in.  According to the Oracle analyst that I am working with, she said is the email set up on our end.  However, we have opened up the relay on our email server to enable