Outlook user Log files & logging [exchange]

Microsoft Outlook supports the logging of the communications that occur 
between Outlook and various types of e-mail servers. These logs can be 
helpful when you troubleshoot problems with the transfer of messages 
between Outlook and the e-mail server. 

Outlook can log the communications with Microsoft Exchange, Post Office Protocol version 3 
(POP3), Simple Mail Transport Protocol (SMTP), Internet Messaging Access
 Protocol (IMAP), and Hotmail servers.  

1. Under the *Tools *menu, click *Options*.

2. On the *Other *tab, click *Advanced Options*.

In OUTLOOK 2010, try File ---> Options ---> Advanced ---> bottom of page

3. Check (enable) or uncheck (disable) the *Enable logging (troubleshooting)
* box.

4. Click *OK *twice and restart Outlook. *Logging Enabled* should appear in
the title

src:http://www.mail-archive.com/exchangelist@lyris.sunbelt-software.com/msg52584.html 

Log file locations

MAPI (Exchange), POP3, and SMTP transports    The log file has the name 
OPMLog.log and is located in one of the following locations: Windows 
Vista

c:\Users\user name\AppData\Local\Temp\Outlook Logging 
Turn off logging

1. On the Tools menu, click Options.
2. On the Other tab, click Advanced Options.
3. Clear the Enable logging (troubleshooting) check box, and then clickOK two times.

For more information http://office.microsoft.com/en-us/outlook-help/what-is-the-enable-logging-troubleshooting-option-HA001230421.aspx

src:  http://answers.microsoft.com/en-us/office/forum/office_2007-outlook/location-of-outlook-log-file/bf33ee2e-a38e-4d22-b422-5d5f6bcae864

src: http://support.microsoft.com/kb/300479