XFOR: Explanation of the Windows 2000 SMTP Banner

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Article ID: 254560 - View products that this article applies to.
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SUMMARY

When a telnet session is initiated to a computer running Microsoft Windows 2000 and Microsoft Exchange 2000 computer at port 25, a banner similar to the following is displayed:
220 smtp01.northamerica.corp.microsoft.com Microsoft ESMTP MAIL Service,
 Version: 5.0.2172.1 ready at  Tue, 29 Feb 2000 18:55:48 -0600
					

MORE INFORMATION

This banner originates from Request for Comments (RFC) 821 section 3.5. The banner can be broken into four separate elements:
  • Reply Code
  • Host
  • Software
  • Date-Time

Reply Code

The reply code in this example is 220.

Reply codes are described in sections 4.2 and 4.3 of RFC 821. A Simple Mail Transfer Protocol (SMTP) reply consists of a three-digit number (transmitted as three alphanumeric characters) followed by some text. The original objective for the reply code is to quickly output a computer-readable response. A formal discussion of reply code theory is outlined in RFC 821, Appendix E. The following are some related points from Appendix E:
2xy--2 as the first value denotes "Positive Completion reply."
x2y--2 as the second value denotes "Connections."
xy0--The last digit, 0, provides the option to give a finer gradation of meaning in each category.

Therefore, 220 means a connection has completed successfully.

Host

In this example the host or computer name is smtp01.northamerica.corp.microsoft.com. This means that the Domain Name Service (DNS) domain name is northamerica.corp.microsoft.com and that the computer name is smtp01. This type of notation is referred to as a Fully Qualified Domain Name (FQDN) because it relates or qualifies the host as a member of a domain that is registered with root DNS servers.
Host: smtp01
Subdomains: northamerica and corp
Domain: microsoft
Root Domain: com
NOTE: For clarification, a node in Active Directory and DNS is any name that is a child to a domain. Therefore, in the preceding example, smtp01, northamerica, and corp are all considered nodes even though smtp01 is a computer and northamerica and corp are subdomains.

Software

The following SMTP service (software) is being used for the information in this article:
Microsoft ESMTP MAIL Service, Version: 5.0.2172.1
This is the default SMTP software that is installed with Microsoft Internet Information Service (IIS) 5.0.

Date-Time

When the originator transmits a message, the Windows 2000 and Exchange 2000 SMTP service attaches the date, time, and Greenwich mean time offset. For additional information, please see the following resources:
Microsoft Knowledge Base article:
156965 XFOR: SMTP Header Time Conflicts with Sent Time on Message
Royal Greenwich Observatory:
http://www.rog.nmm.ac.uk/

Properties

Article ID: 254560 - Last Review: February 28, 2014 - Revision: 4.2
APPLIES TO
  • Microsoft Windows 2000 Standard Edition
  • Microsoft Exchange 2000 Server Standard Edition
Keywords: 
kbnosurvey kbarchive kbinfo KB254560

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