Microsoft Exchange Server SMTPDiag

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1 Microsoft Exchange Server SMTPDiag

2 Contents Microsoft Exchange Server SMTPDiag...1 Contents... 2 Microsoft Exchange Server SMTPDiag...3 SMTPDiag Arguments...3 SMTPDiag Results...4 SMTPDiag Tests...5 Copyright...5

3 3 Microsoft Exchange Server SMTPDiag Updated May 3, 2006 Microsoft Exchange Server SMTPDiag is a diagnostic tool that is used to determine whether Simple Mail Transfer Protocol (SMTP) and Domain Name System (DNS) are configured to reliably deliver mail to an external address. This tool automates some of the steps described in the following Microsoft Knowledge Base articles , HOW TO: Configure the SMTP Connector to Link to Internet Domains in Exchange at , XFOR: Telnet to Port 25 to Test SMTP Communication at , XFOR: How to Obtain Internet Exchanger Records with the NSlookup.exe Utility at Warning Before you use SMTPDiag, be aware that because the network traffic could go over an unprotected network in unencrypted form, an anonymous attacker on the wire could potentially intercept and modify the tool. This would cause incorrect results to be reported by SMTPDiag. You should consider using other sources of information in addition to the reports from SMTPDiag when you make critical troubleshooting or administrative decisions. In other words, do not rely completely on this tool for information. SMTPDiag Arguments SMTPDiag has two required and two optional arguments, and built-in Help. Help is displayed either by providing no arguments, or by using the /? argument. The following table outlines the arguments and corresponding functions described in the Help.

4 4 Usage SMTPDIAG "sender address" "recipient address" [-d target DNS] [/v] Argument sender address recipient address Function Required. Address of a local mailbox. Used to verify SMTP submission and check inbound DNS. Required. address of remote mailbox you are trying to send mail to. Used to verify DNS, and remote mailbox availability. -d target DNS Optional. IP address of target DNS server to use to look up remote MX (mail exchange) records for testing. This is frequently configured as an external DNS server in Exchange Server. The external DNS setting is unavailable for Internet Information Services (IIS) SMTP. /v Optional. Displays additional information about each test. /? Displays help. SMTPDiag Results Results are displayed in four colors, as follows: White text indicates action being taken. Gray indicates informational results. Green indicates a successful test result. Red indicates a failed test result.

5 SMTPDiag Tests SMTPDiag issues DNS queries using both User Datagram Protocol (UDP) and Transmission Control Protocol (TCP) to validate that the queries will succeed. Versions of Windows before Microsoft Windows Server 2003 and Microsoft Windows XP did not support UDP queries. If TCP queries fail, mail will not be delivered successfully. The first thing that SMTPDiag does after verifying syntax is to check the Start of Authority (SOA) record for the remote address domain. The next step is to validate that the local domain MX/A records are resolvable. This test verifies that the sender domain is valid and any bounces can return to the originating server. This test could fail if the domain is not resolvable from inside the firewall. The remote domain MX/A records are then checked also. If this step fails, mail will not route because of issues with DNS. At this point, the network DNS infrastructure must be investigated. When all the DNS records have been successfully queried, the tool tries to connect to all the MX (mail exchange) records that were published for the remote domain on port 25, and tries to do an EHLO, mail from, rcpt to, and quit command. If you use the verbose (/v) option when you run the tool, more information is provided about what each test is doing, as well as detailed results of each test step. 5 Copyright The information contained in this document represents the current view of Microsoft Corporation on the issues discussed as of the date of publication. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information presented after the date of publication. This White Paper is for informational purposes only. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS DOCUMENT. Complying with all applicable copyright laws is the responsibility of the user. Without limiting the rights under copyright, no part of this document may be reproduced, stored in or introduced into a retrieval system, or transmitted in any form or by any means (electronic, mechanical, photocopying, recording, or otherwise), or for any purpose, without the express written permission of Microsoft Corporation. Microsoft may have patents, patent applications, trademarks, copyrights, or other intellectual property rights covering subject matter in this document. Except as expressly

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