TOPIC: PayPal IPN in joomla 2.5

Hi,
i have installed the product on 2 site a old 1.5 joomla and a new 2.5 joomla.
In the old site (1.5) the product work perfect.
In the new site (2.5) using the same paypal address, the payment transaction works but the user sometimes dont receive the mail with the download link
and the admin dont receive the mail.

Hi, I have the same problem, how to sort it out ?