[exim] Hostname rejected

Hi guys,

I have a small problem with Exim4 on Debian Sarge (just to define the
setup, it is probably not related to the distribution at all):
One of my users tries to send a mail which gets rejected because of this
(I purposedly changed the names):
A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es)
failed:

  rainotte@???
    SMTP error from remote mailer after RCPT
TO:<rainotte@???>:
    host savs.dauprine.nl [X.X.X.X]: 504 <totosrv>:
    Helo command rejected: need fully-qualified hostname

While the sending /etc/mailname is "gogo.org" and configuration of Exim
shows absolutely no "totosrv", while "totosrv" is indeed the hostname of
the machine.

Here is the related part of the headers in the original message:
Return-path: <bri.git@???>
Received: from itad-da281073bb.gogo.org ([X.X.X.X]
helo=totoda281073bb)
      by totosrv with esmtp (Exim 4.50)
      id 1FInM3-0002y8-5r; Mon, 13 Mar 2006 14:45:04 +0100
From: "Brigitte" <bri.git@???>
To: "Marc" <rainotte@???>
Date: Mon, 13 Mar 2006 14:46:47 +0100

Anyone could help here?

Thanks