Phantom emails being sent

I am wondering about emails that Outlook 2003 reports it is sending when there are none in the outbox. This happens when send/receive is in progress. I have changed the port number for the outgoing mail server to stop them being sent, but want to find out what’s up. This happens on only one identity I have set up. There are no messages in outbox in Outlook Express, which I don’t use at all.

I am using Norton AV 2003, XP Pro XP2, both Adaware and Spybot S&D, and ZoneAlarm.