Forwarding Mail to External Contacts

Sounds like a problem with the smart host on your Exchange server. Try taking a look at it to make sure it's configured properly.

If no smart host, then most likely RDNS:  Contact the ISP to change them.

I dont think its Reverse lookup thats stopping it. I just tried modifing the address to be my own, as I know what checks our own domain performs. Here is the message header. As you can see, it leaves my own internal exchange server, hits thier spam filter, and continues to thier exchange. Once it gets there, the error message is generated. I have a similar setup working on another domain, with practically all the same features (exchange 2003, barracuda filter etc). The only difference I could find in the settings of exchange was the relay permissions, which on the server which worked, allowing itself to relay. I tried changing this with no effect (though I didnt restart SMTP)

Diagnostic information for administrators:

Generating server: server.domain1.com.au

john.doe@domain2.com.au
#< #5.5.0 smtp;551 This is not a relay host - mail must be to or from host domain.> #SMTP#

Original message headers:

Received: from mail.domain1.com.au ([10.2.100.201]) by
 server.domain1.com.au with Microsoft SMTPSVC(6.0.3790.1830);       Tue, 10
 Jun 2008 11:21:58 +1000
Received: from Unknown [202.182.144.82] by Domain1 SMTP Server - SurfControl E-mail Filter (5.5.0); Tue, 10 Jun 2008 11:21:57 +1000
Received: from server.domain2.local ([172.16.0.8]) by server.domain2.local
 ([172.16.0.8]) with mapi; Tue, 10 Jun 2008 11:21:56 +1000
From: "John Doe" <john.doe@domain2.com.au>
To: Other Guy <Otherg@domain1.com.au>
Date: Tue, 10 Jun 2008 11:21:39 +1000
Subject: test # 3
Thread-Topic: test # 3
Thread-Index: AcjKmFUGIZLTX6TbTB+BCcM5fOMLqA==
Message-ID: <87F84EF14ADBD94AAC96353D171CE37A35BF8BD13B@server.domain2.local>
Accept-Language: en-US, en-AU
Content-Language: en-US
X-MS-Has-Attach:
X-MS-TNEF-Correlator:
acceptlanguage: en-US, en-AU
Content-Type: multipart/alternative;
      boundary="_000_87F84EF14ADBD94AAC96353D171CE37A35BF8BD13Bserver.domain2"
MIME-Version: 1.0
X-SEF-6B7ED60F-97E8-456E-AD8B-5BAB5722E58B: 1
X-SEF-Processed: 5_5_0_191__2008_06_10_11_21_58
Return-Path: john.doe@domain2.com.au
X-OriginalArrivalTime: 10 Jun 2008 01:21:58.0279 (UTC)

I might add, that the exchange 2003 server doing the forwarding, does not use a smart host, and does not have RDNS itself turned on

The error is on their end with their smart host.

You're my hero Simon, I wish I had the same level of knowledge.

My take on this problem, hope to be proved wrong, is that the origin of the message becomes the SMTP server (Exchange) address. The 'to' address is the destination..
So when you automatically forward a message to a ISP, they accept it with open arms..
They may have protection mechanism, but unless you try to relay mail from another account, this shouldn't happen.
Do you have a SMTP log, that will really show us one way or another whats happening..

While the origin of the message becomes the Exchange server, what most antispam solutions are looking at is the From field in combination with the origin of the message. IN this case the ISP is checking that the From field matches a domain in its list that are allowed to relay through their server. As Exchange doesn't touch the From field, it fails this test - hence the rejection.

Simon.

Sorry Simon, just did some test to verify, and all my automatically forwarded emails have a from address which was NOT the originating account, but the account that did the forwarding.
hotmail accepted the email and delivered it intact.

The 'from' address I got from hotmail, was NOT the gmail account I originated the mail from initially.
It was from the account here that I sent it too...

Cant say anything about the antispam component as it wasn't mentioned...

ok, now I have to backtrack, I tried it the otherway and sure enough the from address was from the originating location.

Either way, they did get delivered, but as we send directly so its not an issue for us.

The SMTP logs show that emails were infact getting sent with the from being the originator.

Simon, Do you think they are using an intermediary for outgoings?
and just not aware of it?