Ensuring that a mail server is responding

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This article describes how you can check whether a mail server is responding or not. It explains how to do this in principle and provides links to more extensive troubleshooting material.

Note: This article assumes some technical knowledge of the relevant operating system. If you are unsure, please contact F-Secure support for assistance.

Sometimes it may be necessary to test that a mail server is actually accepting mail and forwarding it on to the correct recipients.

You can test if the network connection to the mail server is working properly by opening a telnet connection to the server. The standard SMTP port is 25. The command to do this is identical on both Linux and Windows operating systems:

[email protected] $ telnet yourmailserver.com 25

If you get a textual response, such as the one below, it means that the network connection is working and the SMTP service is running on that mail server.

Connected to yourmailserver.com.
Escape character is '^]'.
220 mx.yourmailserver.com ESMTP Sendmail 8.12.9/8.12.9; Thu, 12 Jun
2009 10:06:19 +0200

Connection to the host lost or similar error messages mean that the connection was unsuccessful, and you should start troubleshooting by testing the network connectivity.

Extensive troubleshooting information relevant specifically to Microsoft Exchange can be found in Microsoft's Knowledge Base at http://support.microsoft.com/kb/153119.

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