One way this has been accomplished in past, to process this systematically, was built using vb.net program that picks all details from email, parses it and inserts it in excel file, and then stores it in shared location (Sharepoint, ftp, box.com, etc.) every few hours. Eloqua auto synchs then takes the file and fatches it in Eloqua.
Hope this helps, requires some programming, but easily doable. (Advice free of charge )