sieve redirect to foreign email gets “Relay access denied”

[Henry Stack]

On 22-09-2014 23:50, Reindl Harald wrote:
> [...] you need to provide more  informations about your setup and if
 > possible avoid mask IP addresses - where does the smtpd live, where
 > is dovecot and how did you configure the relay at all what postfix
 > version? in case of a recent version -> smtpd_relay_restrictions is
 > configured?

ok here comes the  data
the sieve rule is simple

if header :contains ["subject"] ["redirect"]  {redirect 
"henry at gmail.com"; stop;}

first of all the main issue is the sieve "redirect" to a email address 
on a foreign server. In our case gmail.
(sieve is a part of dovecot, and I found no possibility to make sieve 
more verbose.)
I can make postfix verbose but it just say that relay is not permitted.

to test sieve and the rule I send a email from henry at live.de (Hotmail) 
to my account on the server. henry at example.net and expect it to be 
redirected to henry at gmail.com

The only interesting line in the log-file is still
NOQUEUE: reject: RCPT from mail.example.net[62.78.xxx.xxx]: 554 5.7.1 
<henry at gmail.com>: Relay access denied; from=<henry at live.de> 
to=<henry at gmail.com> proto=ESMTP helo=<mail.example.net>

it say that sieve is trying to make a email FROM henry at live.de TO 
henry at gmail.com and send it via  mail.example.net.
*this is crazzy.*
I think that this is the reason why I get the relay not permitted.
afaik it should envelope the email using  henry at example.net

Even I transform my own server in a open relay and send the email like 
sieve want it to be redirected it will be rejected by the destination 
server because my server is no authority for gmail.

Does somebody know how I can teach sieve to send as envelope ?