Large File Constant Resend

Tried to send a 17.4MB file.  Got the pop up that it is a large file and will take some time to send clicked ok.  Left Program  running overnight. Sent folder shows it was sent 47times!   Recipients have received multiple times 8 reported so far.   It is stuck in the outbox and I do not know how to get it to it to remove so it is still resending.  Using Exchange server via office365.