DOCUMENT:Q115492  02-DEC-1999  [pcmail]
TITLE   :SMTP: Troubleshooting the TCP/IP Layer of the Mail Gateway
PRODUCT :Microsoft Mail For PC Networks
PROD/VER:MS-DOS:3.0
OPER/SYS:
KEYWORDS:

======================================================================
-------------------------------------------------------------------------------
The information in this article applies to:

 - Microsoft Mail Gateway to SMTP, version 3.0 
-------------------------------------------------------------------------------

SUMMARY
=======

If the SMTP gateway cannot connect to the mail routing host or receive incoming
mail, the TCP/IP layer may not be working properly. This article describes how
to troubleshoot the IP and TCP layers.

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

Testing the IP Layer
--------------------

To test the IP layer, use the PING command from the gateway computer up to the
host and from the host down to the gateway computer:

1. Test the network adapter with the loopback IP address:

   ping 127.0.0.1

   If this test fails, then the problem is related to the network interface card
   (NIC).

2. Test the connection on the local subnet:

   ping <ip address>

   where <ip address> is the IP address of a host on the same subnetwork.
   If this fails, then the subnet mask is configured incorrectly.

3. Test the connection to the default gateway:

   ping <gateway ip address>

   where <gateway ip address> is the IP address of the default gateway,
   also known as a router. If this test fails, then you have an incorrect IP
   address for the default gateway, or the gateway is down.

4. Test the connection to a remote subnet:

   ping <remote ip address>

   where <remote ip address> is the IP address of a host on another subnet.
   If this fails, then the connectivity problem is most likely on the remote
   side.

5. Test the DNS name resolution:

   ping <host.domain>

   where <host.domain> is something like smarthost.microsoft.com If this
   fails, then either the DNS entry in the TCP/IP configuration is incorrect or
   the DNS server is having problems providing name service at this time.

If this works, you receive a response indicating how many packets were bounced
off the destination host. Successful completion of these commands means the IP
layer is working correctly.

Testing the TCP Layer
---------------------

To test the TCP layer, use the TELNET command with a "25" after the host ID or IP
address to specify the mail socket. Run it from the gateway computer up to the
host and from the host down to the gateway computer:

   telnet tcpiphost.company.com 25 telnet msmailgwy.company.com 25

NOTE: You can't run the second command unless the gateway is running.

If this succeeds, you receive the response "220 ...." from the destination host.
Type "quit" (without the quotation marks) to end the test. Successful completion
means the TCP layer is working.

NOTE: If you use -cd (debug) and -lacsy (full logging) the 220 response is
recorded in the LOG file.

Additional query words: 3.00 errors

======================================================================
Keywords          :  
Technology        : kbMailSearch kbMailGateSearch kbZNotKeyword3 kbMailGateSMTP300
Version           : MS-DOS:3.0

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS
PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND.  MICROSOFT DISCLAIMS
ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES
OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.  IN NO
EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR
ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL,
CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF
MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE
POSSIBILITY OF SUCH DAMAGES.  SOME STATES DO NOT ALLOW THE EXCLUSION
OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES
SO THE FOREGOING LIMITATION MAY NOT APPLY.

Copyright Microsoft Corporation 1999.