OK, I found the problem. The mails (spam) were deleted on the pc (exchange) also the deleted items and unwanted mails were deleted. OK, all mails mentioned by Backup Exec were deleted. BUT, the mails were still in the information store!!! When I connected thru OWA, the mails were still in the inbox, deleted items,....
When clicking on the mail, preview pane said, can't find information,,,, blah blah blah. After I deleted the mails here in OWA, the backup was successfull!!!!
So after searching a lot... I finally found it...