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Microsoft KB Archive/173903

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Knowledge Base

XFOR: Changing the TCP Port Used for SMTP Mail

Article ID: 173903

Article Last Modified on 10/28/2006


  • Microsoft Exchange Server 4.0 Standard Edition
  • Microsoft Exchange Server 5.0 Standard Edition
  • Microsoft Exchange Server 5.5 Standard Edition

This article was previously published under Q173903


This article tells you how to configure the Microsoft Exchange Server Internet Mail Service (IMS) to use a TCP port other than port 25 to receive SMTP mail. This is a function of the TCP/IP protocol and is controlled by the entry in the Services file in the Winnt\System32\Drivers\Etc directory. This change is required if you are using the new Mail Virus Scan from Symantec; the Symantec product requires forwarding to the SMTP gateway by way of a port other than port 25.


  1. Edit the Services file, Winnt\System32\Drivers\Etc\Services, to specify the port used for SMTP.

    The following example, an excerpt from the Services file, shows removing SMTP from port 25 and enabling SMTP on port 17. Port 17 is normally used for 'qotd' (quote of the day) service.

          smtp 17/tcp mail
          #qotd 17/tcp quote
          #qotd 17/udp quote
          chargen 19/tcp ttytst source
          chargen 19/udp ttytst source
          ftp-data 20/tcp
          ftp 21/tcp
          telnet 23/tcp
          #smtp 25/tcp mail
          time 37/tcp timserver
  2. Telnet ip_address or server_name 17 to verify that the Internet Mail Service is indeed listening on tcp port 17.

Mail Virus Scan is manufactured by Symantec, a vendor independent of Microsoft; we make no warranty, implied or otherwise, regarding this product's performance or reliability.

Keywords: kbinfo kbsetup kbtshoot kbusage KB173903