GAL Corruption?

Here's a more complete example...  The problem has been largely "inside going out emails" and usually (according to reports I've heard) the same domain.

Subject: Mail delivery failed: returning message to sender

This message was created automatically by mail delivery software.

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:

  recipient@otherdomain.org
    SMTP error from remote mail server after RCPT
TO:<recipient@otherdomain.org>:
    host 10.50.204.139 [10.50.204.139]: 550 invalid recipient

------ This is a copy of the message, including all the headers. ------

Return-path: <sender@ourdomain.org>
Received: from [outside IP] (port=55235 helo=ourmachinename.ourdomain.org)  by mx.cbeyond.com with esmtp (Exim 4.62)  (envelope-from <sender@ourdomain.org>)  id 1JJUc1-00049V-Dv  for recipient@otherdomain.org; Mon, 28 Jan 2008 09:05:25 -0500
X-MimeOLE: Produced By Microsoft Exchange V6.5
Content-class: urn:content-classes:message
MIME-Version: 1.0
Content-Type: text/plain;
 charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
Subject:
Date: Mon, 28 Jan 2008 08:52:43 -0500
Message-ID:
<327FF2C7D6C6AC43B51A4435DAD9555801351A47@machinename.ourdomain.org>
In-Reply-To:
<BBB004A63BF99740B7F461BBFD6220F0033F3135@recipient.otherdomain.local>
X-MS-Has-Attach:
X-MS-TNEF-Correlator:
Thread-Index: Achg+hyXBfvv9V5nQe+CQ6qmhpMWAgAuudcg
References:
<BBB004A63BF99740B7F461BBFD6220F0033F3135@recipient.otherdomain.local>
From: "firstname lastname" <sender@ourdomain.org>
To: "firstname lastname" <recipient@otherdomain.org>

LTWadmin,

Usually when i see this I do a bit of investigation.

Namely can i send an email manually to this offending server?
http://www.yuki-onna.co.uk/email/smtp.html

And then i investigate any anti spam facilities
https://www.experts-exchange.com/questions/22098983/550-Invalid-recipient.html

JimboEfx

OK - The Telnet thing was cool - didn't know you could do that.  Here are the results:

220 machinename.ourdomain.org Microsoft ESMTP MAIL Service, Version: 6.0.3790.1830
ready at  Thu, 31 Jan 2008 17:22:58 -0500
HELO ourdomainname.org
500 5.3.3 Unrecognized command
HELO mail.ourdomain.org
250 machinename.ourdomain.org Hello [192.168.11.8]
MAIL FROM: myname@mydomain.org
250 2.1.0 myname@mydomain.org....Sender OK
RCPT TO: mail@targetserver.org
550 5.7.1 Unable to relay for mail@targetserver.org...

So this indicates the mail server has refused to relay mail for us?

provided you have smtped to their mail server directly (not your own becuase it is usually realy secured!) then this would indicate a smtp error on their end.

Of course to complicate matters some anti spam products will send valid smtp error codes if they want to reject your message - even though it is the incorrect use of that code!

Best to get in touch with their it staff and have a chat.

This part indicates an attempt to send mail to the target server from my own yes?

MAIL FROM: myname@mydomain.org
250 2.1.0 myname@mydomain.org....Sender OK
RCPT TO: mail@targetserver.org
550 5.7.1 Unable to relay for mail@targetserver.org...

when you started the telnet you did

telnet someservername 25
ehlo blah
mail from:blah@
rcpt to: blah@
data
blah
.

the someservername should the recipients mail server, not yours!

To found out their mail server you need to find their mx record http://www.mxtoolbox.com/

telnet to the lowest priority mx record and then try again.

HTH

Turned out to be the ISP...