In case you need to return to the original source of records there's the facility for adding external references on the Sources tab of a Survey. Maybe heavy users utilise this, maybe not, but it's handy for Recording Schemes. Here's a tip:
Save the incoming email as an HTML file, giving it the filename [date reversed]_[Individual] and pop that into External References.
For single records that might be all that's needed but for emails that have attachments an EDMS would be handy too.
You don't need a top of the range EDMS, the iMatch5 image manager from photools.com will do the trick. If you stack (an iMatch feature) the saved html email file with all the attachments and working files you produce up to the point of a spreadsheet ready for R6 import in a separate "Records" iMatch database then that single R6 email External reference will take you to all the related work. iMatch will let you categorise such work and work flows too with its user-configurable categories, tags and the file moving facility which keeps all buddy files created by "stacking" together.