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Q245787: XFOR: SMTP Error Message: 550 Invalid Domain

Article: Q245787
Product(s): Microsoft Exchange
Version(s): winnt:4.0,5.0,5.5
Operating System(s): 
Keyword(s): exc4 exc5 exc55
Last Modified: 04-DEC-1999

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The information in this article applies to:

- Microsoft Exchange Server, versions 4.0, 5.0, 5.5 
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SYMPTOMS
========

If you send outbound Simple Mail Transfer Protocol (SMTP) mail, a non-delivery
report (NDR) similar to the following is displayed:

  550 Invalid Domain.

The following NDR is also logged in the application event log:

  Event ID: 4031
  Source: MSEXCHANGEIMC
  Description:
  The message could not be delivered. The destination server reported: 550
  Invalid Domain.

CAUSE
=====

This problem may be caused by a Domain Name System (DNS) record that points to
the wrong mail host for a certain domain. This incorrect DNS information causes
Exchange Server to connect to the wrong mail host when you try to send mail to a
recipient in another domain, which generates the error message in the "Symptoms"
section of this article.

This problem may also be caused by the incorrect configuration of an "echo
firewall." The echo firewall is an advanced device that verifies every command
that is sent to the Exchange Server computer. This type of firewall cannot be a
Network Address Translation (NAT) or packet-filter device. If you incorrectly
configure this firewall so that it does not accept mail from a domain that it
needs to accept mail from, the error message in the "Symptoms" section of this
article may also be displayed. The mail never resides on the firewall, but
passes through it.

RESOLUTION
==========

Use the NSLookup utility to make sure that the MX and A records of the Exchange
Server domain on the Internet are correct.

If the problem is related to the incorrect configuration of an echo firewall,
then correct the configuration of the firewall.

MORE INFORMATION
================

The error message in the "Symptoms" section of this article is closely related
to the following Exchange Server generated error message:

  550 Relaying is prohibited

The message route of this topology is:

  Sending Exchange Server ----- Internet ------ Firewall ----- Mailhost

The SMTP conversation of this problem may look like the following log:

  

  A connection to 10.1.1.25 was established.

  <<< IO: |220 firewall.expedia.com Generic SMTP handler

  <<< 220 firewall.expedia.com Generic SMTP handler

  >>> EHLO ExchangeSending.microsoft.com

  <<< IO: |500 Command unrecognized

  <<< 500 Command unrecognized

  >>> HELO ExchangeSending.microsoft.com

  <<< IO: |250 firewall.expedia.com talking to
  mailhost.expedia.com [157.5.1.4])

  <<< 250 firewall.expedia.com talking to mailhost.expedia.com ([157.5.1.4])

  >>> MAIL FROM: <bob@microsoft.com>

  <<< IO: |250 <bob@microsoft.com>: Sender Ok

  <<< 250 <bob@microsoft.com>: Sender Ok

  >>> RCPT TO:<vincent@expedia.com>

  <<< IO: |550 Domain invalid

  <<< 550 Domain invalid

  >>> QUIT

  <<< IO: |221 firewall.microsoft.com closing connection. Goodbye!

Additional query words: 4031 3010 Invalid Raptor Secure Gateway

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Keywords          : exc4 exc5 exc55 
Technology        : kbExchangeSearch kbExchange500 kbExchange550 kbExchange400 kbZNotKeyword2
Version           : winnt:4.0,5.0,5.5
Issue type        : kbprb

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