Log into PayPal, click PROFILE, then look under SELLING PREFERENCES> There you will see (amongst others)
# Payment Receiving Preferences
# Instant Payment Notification Preferences
# Website Payment Preferences
# Encrypted Payment Settings
In Website Payment Preferences, make sure AUTO RETURN is turned on. Mind you, none of this is helping with the issue I'm having where PayPal payments aren' being completed, the order appears in the admin panel but I get no email notification. :(