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Microsoft KB Archive/100709

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Knowledge Base

Article ID: 100709

Article Last Modified on 10/30/2006


  • Microsoft Mail Gateway to SMTP 3.0
  • Microsoft Mail Gateway to SMTP 2.1

This article was previously published under Q100709


Microsoft Mail Gateway to SMTP may display this message:

ERROR Network_read: Lost network connection
SMTP_recv: system error


This error message appears if:

  • An error at the TCP or IP layer has occurred.
  • The other host has gone down.
  • The network between the Gateway computer and the other host has gone down.
  • The other host may require that the PUSH flag be sent to push the SMTP packet up to the SMTP software, instead of remaining in the incoming buffer.


You can test these possible causes by attempting to telnet to port 25 of the smarthost and resending the message. This can usually be done by pressing SPACEBAR and typing "25" (without the quotation marks) after the IP address on the telnet command line.

If the error message appears frequently, check the network with a protocol analyzer to determine the exact problem.

NOTE: Mail sent to IBM TCP/IP Version 2, Release 2 may result in this error message if the PUSH flag is not set. FTP's pc/TCP automatically sets the PUSH flag for outgoing packets. For Microsoft LAN Manager TCP/IP, please contact Microsoft LAN Manager support for information on the availability to automatically set the PUSH flag.

For Microsoft LAN Manager TCP/IP, ensure you are using version 2.2b (dated 2/1/94, 42,716 bytes) or later of the file TCPTSR.EXE. By default, TCPTSR.EXE is found in the LANMAN.DOS\DRIVERS\PROTOCOL\TCPIP directory. Then add the parameter ForcePushBit=1 to the [TCPIP] section of the PROTOCOL.INI file. It defaults to 0, but when it is set to 1, it causes the PUSH bit to be set on every outgoing packet.


The following file is available for download from the Microsoft Download Center:

For additional information about how to download Microsoft Support files, click the following article number to view the article in the Microsoft Knowledge Base:

119591 How to Obtain Microsoft Support Files from Online Services

Microsoft scanned this file for viruses. Microsoft used the most current virus-detection software that was available on the date that the file was posted. The file is stored on security-enhanced servers that help to prevent any unauthorized changes to the file.

Additional query words: 2.10 3.00 ERRMSG smart host push flag

Keywords: kbdownload kbgraphxlinkcritical KB100709