Can't pipe email

I followed the tutorial to do email piping to a PHP script. When I send an email, it’s bounced back and I get this error message:

[quote]Final-Recipient: rfc822;
Original-Recipient: rfc822;
Action: failed
Status: 5.0.0
Diagnostic-Code: X-Postfix; maildir delivery failed: create
Disk quota exceeded[/quote]

My PHP script is empty so it’s not a coding issue… Here’s the content of my .forward.postfix file:

I don’t know why it says my disk quota is exceeded. My mailbox and my user have both plenty of space… Any idea? Thanks.