Analyze Microsoft Telnet configuration problems

Source: Internet
Author: User
Tags valid email address nslookup fully qualified domain name

In Microsoft, Telnet is disabled by default. Therefore, we need to manually start this service. Next, let's analyze some issues about Microsoft Telnet settings. We usually encounter many problems. Here we will mainly introduce the port problems in Microsoft Telnet settings. So I hope it will help you. Telnet to port 25 to test smtp communication _ exchange server this article describes how to telnet to port 25 on a computer running the Simple Mail Transport Protocol (SMTP) Service to solve SMTP communication problems. By default, the SMTP listening port is 25.

You can select the following troubleshooting steps based on your problem type. For example, if you encounter problems when sending emails through SMTP between two Microsoft Exchange 2000 Server servers, you can test the SNMT connection by using Telnet on the sending server to connect to port 25 on the target server. Or, if you encounter problems when receiving SNMT emails from the Internet, follow the steps listed in this article, test the connection between a host residing on the Internet but not on your network and your SNMT server. For more information, the Microsoft product line contains multiple different SNMT variants. The SNMT service of Microsoft Windows product line is included in Internet Information Service (IIS), while in Microsoft Windows NT Server 4.0, SMTP service is included in Option Pack. In a newer version of Windows, IIS has been integrated into the operating system, and you can use "add or delete programs" in "Control Panel" to add IIS. In addition, both Exchange 2000 and Microsoft Exchange Server 2003 use the existing SNMT service and other functions in IIS. Microsoft Exchange Server versions 4.0, 5.0, and 5.5 all contain their own SNMT versions in the form of Internet Mail Connector (IMC) or Internet Mail Service (IMS ).

Note: In Exchange 5.0 and later versions, Internet Mail ctor (IMC) is renamed as Internet Mail Service.

Before starting a Telnet session, you must have a complete SNMT email address for the target user to send the test email. The email address must be in the following format: you can also have a fully qualified domain name (FQDN) or IP address (for example, for the server computer that runs the SNMT service ). If the server is in your organization, you may already have this information. If the server is an external server, the easiest way to find this information is to use Nslookup.exe to find the DNS records containing this information.

For more information about NSlookup, click the following article number to view the article in the Microsoft Knowledge Base: 200525 use NSlookup.exe to obtain other information about how to obtain Internet Mail exchanger records, click the following article number to view the article in the Microsoft Knowledge Base: 203204 XFOR: how to obtain Internet Mail exchanger records to ensure that SMTP is enabled on the server on which the SNMT service is running. To test whether SNMT has been started, you can run the basic test listed in this article and verify that you will receive the 220 message from the remote server. This will also verify that SNMT is running.


Some Telnet applications require you to enable the local ECHO function to view the entered commands. To perform this operation in a Microsoft Telnet session, type set local_echo at the command prompt.

In Microsoft Windows XP, type set localecho instead of set local_echo.

Perform the following steps to ensure the communication between the host and the remote SNMT server. If you receive the following error message after you type any of the following commands, it means that the SNMT server cannot identify the entered content due to a syntax error or command error: 500 Command not recognized check this Command and type it again, or verify that you are communicating directly with the MicrosoftSNMT server.

Note: Microsoft Telnet does not allow you to use the Backspace key. If an error occurs while typing, you must press Enter to start typing a new command.

In the following steps, run Telnet from the command line. To open the command line, click Start, click Run, Type cmd in the open box, and then click OK ".

1. You can start a Telnet session by using the Telnet command in the following format:

Note: Press Enter after each line of content is entered. For example, enter telnet 25. Note: You can replace the server name with the IP address or fqdn of the snmt server you want to connect. Remember to press Enter after entering each command.

If this command works, you will receive a message similar to the following from the SNMT server: 220 Microsoft Exchange Internet Mail Connector Note: because there are many different versions of MicrosoftSNMT or third-party SNMT servers, therefore, you may receive different messages from the receiving server. However, you will certainly receive a 220 message containing the server's FQDN and SNMT version. In addition, all versions of Microsoft snmt contain the word "Microsoft" in the 220 message.

2. run the following command to Start Communication: EHLO Note: You can use the HELO command, but EHLO is a verb that extends the SNMT verb set. All current Microsoft implementations of SMTP support this verb set. Unless you think there is a problem with the SNMT extension verb, it is best to use EHLO.

If the command succeeds, you will receive the following message: 250 OK

3. type the following command to notify the sender of the MAIL to receive the SNMT server: mail from:

Note: This address can be any SNMT address you want to use, but you 'd better consider the following:

1. some smtp mail systems filter emails Based on the mail from: address, and prohibit some IP addresses FROM connecting to the snmt mail system, or if the connection IP address does not match the domain of the snmt mail system, it also disables this address from sending emails to the SMTP mail system. In this example, the domain is

2. if you do not use a valid email address when sending an email, you cannot determine whether there is a problem when sending the email because the undelivered report (NDR) cannot reach an invalid IP address. If you use a valid email address, you will receive the following message FROM the SMTP server: 250 OK-MAIL FROM 4. type the following command to receive the recipient of the SNMT server notification message.

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