php email return path problem

[jeboy]

I have setup an email which will be the return path of the email that i sent (eg. [email protected]). And all incoming emails to that email (ie. [email protected]) will be forwarded to a script that will fetch those emails and enters it to the database. When I send an email to ([email protected]) it works as expected, it redirects the email to my script but when I purposely send a message to an invalid email or to non existent email, it just bounce back to ([email protected]) and it doesn't redirect to my script. What should be done? Please help.