Someone is probably going to ask you to answer the questions in the posting tips, if they haven't already done so while I'm typing this.
Problems with paypal emails usually relate to the paypal module. What payment module are you using for paypal? There are 3 -
Paypal Express - seems to be the recommended one, doesn't have issues too often.
Paypal Website Payments Standard IPN - has a slight tendency to vomit all over itself after a hard night of processing payments, usually falls asleep on bathroom floor before sending any emails. It's recommended that you avoid this one.
Paypal Website Payments Pro - I know absolutely nothing about this one!
Usually when people complain about this issue it's because they're using the IPN module instead of the express, but I'da thought that install option would have disappeared with 1.5.0 so I may be (probably am) wrong....