[Dovecot] Pure virtual user and RT3.x

[Egbert]

Hi,

I have mailsystem with virtual users only (/home/vmail/domain/user). I 
need to integrate RT3.x (a ticketing system). I have installed the 
client but I need to send mail to a pipe. Rt wants me to insert:

|/usr/bin/rt-mailgate --queue bla --action bla --url http://bla.bal/

In /etc/postfix/aliases. That does not work for me.

What is the right way to achieve that mail to rt at mydomain is sent to the 
pipe? Should I install, configure and use a Sieve filter? I have none 
installed at the moment. Or are there other (simpler?) ways?
TIA
Egbert Jan