Originally Posted by Babaganoosh

Forgot all about this thread. Hope you got it going. If not try this

check postfix main.cf and make sure your subdomain is listed. I think it needs to be defined in virtal_alias_domains. never tried it with a subdomain so not too sure on this

/etc/postfix/virtual
[email protected] babaganoosh

then edit your /etc/aliases
babaganoosh: "|/usr/bin/php -q /path/to/your/script"

Then run the following commands
postmap /etc/postfix/virtual
/etc/init.d/postfix restart
newaliases

This works on Ubuntu 10.04

Edit: You do not need to set up a system user for your alias.