[RCU] Mail_Mime Envelope-To header

Hi everyone,

currently I'm working on a plugin for Roundcube using some functions of Mail_Mime.

At one point (Hook: message_before_send) I have to replace the recipient of the mail with another one, so I use

$message->get(); $message->headers(array('To'=>implode(',', $recipients)), true);

This code is doing well. But there still is the "Envelope-To"-Header which I can't replace like follows:

$message->headers(array('To'=>implode(',', $recipients), 'Envelope-To'=>implode(',', $recipients)), true);

Am I totally wrong? I'm just stuck with this. Can anyone help?

Sincerely Dominik