For high volume scanning requirements we recommend and implement solutions from Kofax (see the Kofax page). 

Most of these solutions are integrated with existing line of business systems to extract additional metadata for inclusion with the scanned image for future identification. Workflow is also frequently part of the solution to route scanned documents for processing and storage in the correct location.

Deltascheme have built a range of solutions from digital mailrooms for the scanning of inbound mail to automated invoice capture using the Kofax Transformation module.