Inviando una email con asp.net v1.1 in formato HTML solo ad alcuni provider come T-ONLINE.DE il messaggio non viene consegnato e torna una ricevuta di errore.
Cosa può causare questo errore?

Mail delivery failed: returning message to sender

|------------------------- Failed addresses follow:
|---------------------|
<xxxxx@t-online.de>
554 5.6.0 Message contains NUL characters

|------------------------- Message header follows:
|----------------------|
Received: from 12reverse..it ([xx.xx.87.12]) by mailin07.aul.t-online.de
with esmtp id 1JoGYK-03JPX60; Tue, 22 Apr 2008 13:20:48 +0200
Received: from mail pickup service by 12reverse.it with Microsoft SMTPSVC;
Tue, 22 Apr 2008 13:20:36 +0200
Thread-Topic: Ordine web
X-ORI_ip: xx.xx.94.224
X-Company: Marco-ITALY
thread-index: AcikauLuiDDS5RcsQKWwE5WdCmmSWg==
From: <xx@xxxx.it>
To: <xxx@t-online.de>
Subject: Ordine web n. 220
Date: Tue, 22 Apr 2008 13:20:36 +0200
Message-ID: <DA712619F82248A998F19BBFF5B9E4B5@G501>
MIME-Version: 1.0
Content-Type: multipart/alternative;
boundary="----=_NextPart_000_0023_01C8A47B.A677C960"
X-Mailer: Microsoft CDO for Windows 2000
Content-Class: urn:content-classes:message
Importance: normal
Priority: normal
X-MimeOLE: Produced By Microsoft MimeOLE V6.00.3790.4133
X-OriginalArrivalTime: 22 Apr 2008 11:20:36.0243 (UTC) FILETIME=[E306EE30:01C8A46A]

|----------- Message text follows: (body too large, truncated)
|----------|
This is a multi-part message in MIME format.

------=_NextPart_000_0023_01C8A47B.A677C960
Content-Type: text/plain;
charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable

Re-view Order =09
Gesamte Bestellung einschli=DFlich Mehrwertsteuer ?. 207.00 =20
Skonto 0 % =20
Erm=E4=DFigter Gesamtbetrag einschlie=DFlich Mehrwertsteuer ?. 207.00
Transport

Ho provato con questa istruzione

mail.Body = BodyStr.Replace(Chr(0), String.Empty)

ma nulla torna indietro lo stesso.
Ho dovuto aspettare un altro cliente t-online per evitare di tempestare il precendere di email prova.

Non so che fare...