Okay, so I have Norton Antivirus installed. You know how when you send mail, the NAV box pops up in the lower right-hand corner saying it's scanning outgoing mail? Well I noticed that it was doing that when I had no mail in my outbox. I scanned with NAV and couldn't find anything.
A couple of days ago, I decided to turn off all the smtp servers in my Outlook email accounts and lo and behold I start getting messages about sent mail (that I didn't write) not being sent because of problems with the server.
I've turned off receipts in my mail options and can't figure out what might be generating these mysterious outgoing emails. Any ideas?