In Outlook 2003 if I send a large attachment, 3+ MB, it will often repeat sending until I can delete it from the oubox. I have to turn off Outlook and restart it to delete the message from the outbox.

I have a similar issue in Outlook 2002 V 10.... When my inbox gets full, it will not allow me to delete messages to the deleted file folder, only immediate delete (ctrl/del). The last message in my outbox at that time whether with or without an attachment, gets resent 100's of times and I can find no way to stop the sending.