[Exim] Envelope-to header max. one address ?

I'm aliasing several domains to 1 user mailbox, and I would like
to have the Envelope-to header show the original recipients - as
it supposedly does.

But whatever I try Envelope-to always shows only one recipient.

Very small example, in reality my aliases are domain-based, but
the result is the same...

#/etc/aliases:
testalias1: miquels
testalias2: miquels

$ mutt testalias2 testalias1
[enter test message]

result:

Return-path: <miquels@???>
Envelope-to: testalias2@???
Date: Mon, 4 Mar 2002 17:46:18 +0100
From: Miquel van Smoorenburg <miquels@???>
To: testalias2@???, testalias1@???
Subject: test
Message-ID: <20020304174618.A9187@???>

As you can see, there's only one address in the Envelope-to:
header.

How can I fix this? It's probably due to exim removing duplicate
addresses, or something ?

Mike.
--
Computers are useless, they only give answers. --Pablo Picasso