This banner originates from Request for Comments (RFC) 821 section 3.5. The banner can be broken into four separate elements:
- 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.
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.
Subdomains: northamerica and corp
Root Domain: com
: 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
, and corp
are all considered nodes even though smtp01
is a computer and northamerica
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.
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:
XFOR: SMTP Header Time Conflicts with Sent Time on Message
Royal Greenwich Observatory: