About a year ago, I had a similar experience. I was in tears. I called my provider who told me that this had happened when I had interrupted a message that had not completely been sent so the necessary ending message had not been received by the system which made it send the whole batch over and over.
Here is the solution that works with my particular E-mail program of Outlook Express
Go to Start=then RUN
type in "telnet spiritone.com" put your own server instead of spiritone.com
this will connect you to the server or internet==you go somewhere?
then "log in: "laurel" enter
Password: " " enter
Then you will see a number of selections that will allow you to
scan= look at the stuff backed up in your mailbox
select and delete as you wish
delete the whole batch that is backed up
Hope this works for you