Microsoft Outlook 20003

Hi,
I’m using Microsoft outlook 2003. I’m also running Norton Anti-Virus.I noticed every once in a while an e-mail is sent. The norton anti-virus screen pops up for a split second to show it scanned an outgoing e-mail. This is a e-mail I did not send. when I check the sent log,it shows nothing being sent.I tried running spyware and checked for any virus. Did not find anything. I was wondering if there was some kind of log from Outlook I could check.
Any help would be appreciated.