Microsoft Exchange Server 2003 – SMTP Logs

Introduction to Exchange 2003 Server SMTP Logs

In Exchange 2003 server, SMTP (Simple Mail Transport Protocol) has many shades of meaning.  On this page I use the word SMTP in the context of understanding logs.  These SMTP logs contain records of each server’s email conversations.  However, bear in mind that the acronym SMTP has other connotations, for example, SMTP Virtual Server, the SMTP service in IIS and SMTP routing connections.

Topics for Exchange 2003 SMTP Logs


Creating SMTP logsSMTP Logging, ODBC, Microsoft IIS, W3C Extended Log File format

Let us take the situation where one server is collecting email, but only intermittently.  We would like to understand the SMTP conversation between Exchange 2003 servers and so discover the cause of the problem.  This is a classic job for SMTP protocol logging.

There are two ways of navigating to the diagram opposite, either visit IIS, or launch the Exchange System Manager and navigate to Protocols folder and then to the SMTP server icon.

Choice of 4 SMTP log formats

You have 4 methods for collecting SMTP conversations:

  • W3C Extended Log File Format
  • NCSA Common Log File Format
  • ODBC Logging
  • Microsoft IIS Log File Format

The default log format is W3C Extended.  This format is a great way to get started with SMTP logging.  However, if you need more extensive search capabilities and you have a database such as SQL, then select ODBC Logging.

I have to admit that I have yet to find a use for NCSA common log file format.  The Microsoft IIS Log File Format is O.K. but lacks the flexibility and customization of the W3C format.

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W3C Extended Log File FormatSMTP Logs W3C Format

The W3C format is my favourite SMTP logging method.  In particular, I like the flexibility provided by extended properties on the advanced tab.  Here is the output of log where I chose to record the client IP, the SMTP method, and the reply code or sc-status.

#Software: Internet Information Services 6.0
#Version: 1.0
#Date: 2005-02-03 12:40:23
#Fields: time c-ip cs-method cs-uri-stem sc-status


#Software: IIS v 6.0 (Probably from a Windows Server 2003)

#Version: 1.0 Means W3C Extended log format (Not ODBC)

#Date: Probably USA day month format.
#Fields: As the name field suggests the column heading for the data recorded. Example, cs-uri-stem means the resource requested.

Understanding the SMTP codes

s- means server, whereas sc- means server to client.  For example sc-bytes means the number of bytes sent by the server.  c- I expect that you have already guessed, c- means client.

Mail Transfer conversation

#Fields: time    c-ip    cs-method  sc-status
     14:13:11    HELO      250
     14:13:13    MAIL      250
     14:13:19    RCPT      250
     14:13:29    DATA     250
     14:13:31    QUIT      240

Possible SMTP methods found under cs-method: HELO, MAIL, RCPT, DATA and QUIT.

sc-status value of 250.  Server to client transactions, which return a value 250, means O.K.  (421 would mean service not available, or 554 would mean transaction failed).

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Finding the Log Output

Finding the SMTP logs is not trivial.  Whereas many programs output their events to the Application log, SMTP Logs are to be found under the "%windir%\system32\logfiles\SMTPSVC1*.  Typically, you get a one log for each day, so double click the file that you are interested in and notepad will open the log and display the data.

All W3C Extended Log File Format files begin with ex, for example exyyddmm.log

* Corrected by Juha (Guy thought it was %windir%\system32\logfiles\W3SVC1)

SMTP Logs Exchange Server  If you click Start (Menu), Run, Logfiles (Type), now you should see the Windows Explorer open the correct directory to find your SMTP logs.

What to look out for
Open Relaying – Symptoms your server is sending mail that you do not recognise to an external server.  Moreover it’s not just one email but a whole load of possible spam messages.

SMTP Microsoft Exchange Server 2003 – SMTP Logs

This page is to designed to help you understand SMTP logs.  Exchange relies on IIS to provide protocol logging.  Of the four formats available, W3C Extended Log File Format provides the greatest choice of output.  ODBC logging is useful if you have a SQL database and need to query a large amount of data.  To check your SMTP logs, click Start (menu), run, logfiles.

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See Also