mixture, what do you mean by that. A senior moment I think but I couldn't figure it.
Spamcop as in spamcop.net
Its a website where you can copy/paste the raw source of an offending email and it does all the analysis for you and automatically proposes the correct email addresses to report to (and will even send reports too).
Very handy.... and you get a reasonably generous amount of usage for free.
If, on the other hand, you meant "what is the raw source ?" ... by that I meant the text version of the email that contains the Header and other lines that are normally hidden from you in the normal email interface.