I have the following problem:

We have to send e-mails to Partners of our company, but when we try this we
get Mails back like the following: (the mail-address is correct!)

Undelivered mail : Unknown user: user@partner.com

------ part of mail received ------
Received: from [] by mail.ourcomp.de;Wed, 16 Aug 2006 12:57:59 GMT
Received: from DO-TT1-MTA by gw.ourcomp.de
with Novell_GroupWise; Wed, 16 Aug 2006 14:58:00 +0200
Message-Id: <44E33268.9447.0098.0@ourcomp.de>
X-Mailer: Novell GroupWise Internet Agent 7.0.1
Date: Wed, 16 Aug 2006 14:57:45 +0200
From: "Username"
Subject: Testmail
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable
Content-Disposition: inline

The recipient Mail-Server is using greylisting and we're using GroupWise
7.0.1 on a NetWare6.5 Server and the line to internet is through a border
manager server.

If I use telnet to contact the extern Mail server I could send mails
through with waiting 10 Minutes because of greylisting.

Also we have problems sending mails to ohter servers (without greylisting)
like arcor.de but only with loose adresses.
Could this perhaps be a problem in our system? But Where? And why?

Has anyone any ideas what the problem could be?

Thanks for help,