[Dovecot] How to pipe to external program

[Egbert]

Hi,

Second try...
I have mailsystem with virtual users only (/home/vmail/domain/user). I 
need to integrate RT3.x (a ticketing system). I have installed the 
RT-client but I need to send the mail to an extrnal program. 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 becase my local delivery agent is dovecot. The 
Sieve plugin seems not capable to forward to a external program.

What is the right way to achieve that mail to rt at mydomain is sent to the 
pipe?

TIA
Egbert Jan