I googled "outlook 2003 sending messages but there's nothing in my OUTBOX" which pointed me to a tech support site that I haven't been able to stumble upon ever ever again. Well I downloaded a very clever VEEEERY dangerous utility called MDBVU32.EXE. Apparently there were "stuck read-receipts" in my outbox.
I followed the instructions very carefully, including making a backup of my OUTLOOK.PST and ARCHIVE.PST files, and it worked!! It wasn't long and another read-receipt got stuck, and I tried to operate the MDBVU32.EXE without reading the instructions. I deleted my default folders, but that's no problem, is it? I made a backup of my PST folders!!
Hah! That's what I thought... Outlook won't start - it says UNABLE TO OPEN YOUR DEFAULT E-MAIL FOLDERS. THE OPERATION CANNOT BE PERFORMED BECAUSE THE OBJECT HAS BEEN DELETED. I copied my backed up PST files back to where they belong and NO GO. Outlook doesn't want to know. I ran a detect and repair, and a SCANPST.EXE and it just doesn't like me in the least any more.
PLEASE HELP!